CN114888304B - A method for manufacturing a composite porous structure liquid-absorbing core - Google Patents

Abstract

The invention discloses a manufacturing method of a composite porous structure liquid suction core, and relates to the liquid suction core processing technology. Firstly, designing a three-dimensional skeleton structure model, then, guiding the designed three-dimensional skeleton structure model into a 3D printing system, taking metal powder as a raw material, and printing by adopting a laser sintering process to obtain a liquid absorption core skeleton structure containing micro-pores; after printing, introducing oxygen into the cavity of the printer, wherein the oxygen content is 2% -16%, adjusting the parameters of a printer laser, carrying out surface laser printing on the printed liquid absorption core skeleton structure containing the micro-pores, and repeating the steps for 2-10 times to obtain the hydrophilic-hydrophobic controllable liquid absorption core with the composite porous structure. The manufacturing method is simple, has less material consumption, can improve the capillary force of the liquid suction core, reduces the heat transfer resistance, has convenient regulation and control of the surface wettability, and strengthens the heat transfer and condensation efficiency of the liquid suction core.

Description

A method for manufacturing a composite porous structure liquid-absorbing core

technical field

The invention belongs to the technical field of liquid-absorbent core processing, and in particular relates to a method for manufacturing a liquid-absorbent core with a hydrophilic-hydrophobic controllable composite porous structure.

Background technique

With the development of miniaturization, integration and high performance of electronic equipment, the degradation of equipment performance caused by high heat flux gradually appears, and the problem of thermal management of electronic equipment is becoming more and more serious. When the operating temperature of electronic equipment exceeds the rated operating temperature by 10°C, its reliability is reduced by 50%. The ever-increasing demand for heat dissipation has become a bottleneck restricting the application of electronic components. Therefore, phase change heat transfer devices such as heat pipes and vapor chambers are widely used for effective thermal management of electronic products due to their high thermal conductivity, high stability, high reliability, and high cooling capacity. The liquid wick generates capillary pressure, which is then used to drive the working fluid from the condenser to the evaporator to maintain the operation of the cooling system. It is the most critical component of the phase change cooling system, and its performance directly affects the heat pipe or uniform temperature plate cooling performance. At present, the common types of wicks mainly include metal powder sintered wicks, wire mesh wicks and groove or channel wicks.

The existing manufacturing method of the liquid-absorbing core is mainly prepared by a sintering method, and the sintering materials are metal powder, wire mesh and metal fiber. The metal powder sintered liquid absorbent core has the advantages of high mechanical strength and strong capillary force, but the liquid absorbent core has low permeability and large fluid flow resistance, which is not conducive to the gas-liquid separation of the phase change of the working medium when the liquid absorbent core is working; at the same time, the preparation cycle Long, it is necessary to cooperate with machining the corresponding mold to control the size of the liquid-absorbing core, and the aperture and porosity are uncontrollable. The screen-type liquid-absorbing core has the advantages of high porosity, simple processing technology and low cost, but the liquid-absorbing core has the disadvantages of low capillary force and large thermal resistance between different wire mesh layers, and the heat transfer effect is poor. Except for the liquid-absorbing core prepared by the above-mentioned sintering method, the groove or channel-type liquid-absorbing core formed by machining has low capillary force and is not suitable for high heat flux density electronic equipment. In addition, the regulation of the hydrophilicity and hydrophobicity of the liquid-absorbent core plays a key role in improving the heat transfer performance of the heat pipe vapor chamber. However, the hydrophilicity and hydrophobicity of the existing liquid-absorbent core needs to be combined with surface post-treatment. The production process is complicated and it is not convenient for quantitative production.

The composite structure liquid-absorbent core combines the characteristics of various liquid-absorbent cores, and makes up for the shortcomings of the above-mentioned liquid-absorbent cores. For this reason, Patent No. CN104075603A discloses a heat pipe composite liquid-absorbing core and its preparation method. The liquid-absorbing core is composed of a metal outer sleeve and a metal porous flow channel. At the same time, the metal porous flow channel provides the working fluid return channel, which reduces the liquid return resistance, thereby improving the heat transfer performance of the heat pipe. However, due to the need to combine the wire cutting method to make molds in advance, the process is cumbersome, and the micropores of the liquid-absorbing core are randomly distributed, which is not conducive to gas-liquid transportation. Patent Publication No. CNC104776742A proposes a manufacturing method for a composite liquid-absorbing core, the liquid-absorbing core structure adopts the form of combined sintering of wire mesh and foamed copper or copper powder, and sinters foamed copper or copper powder on at least one surface of the wire mesh layer. The procedure of this patent is cumbersome and complicated, and the pore structure cannot be well controlled. Patent Publication No. CN110385436A discloses a metal liquid-absorbent core with multi-aperture structure characteristics and its manufacturing method. The microstructure formed by the powder bonding gap made by the liquid-absorbent core can meet the needs of improving capillary performance, but the micropores are random. Combined, the uncontrollable pores lead to large resistance to gas-liquid flow in the liquid-absorbing core, which is not conducive to the heat dissipation requirements of high heat flux.

Contents of the invention

Aiming at the deficiencies of the prior art, the invention provides a method for manufacturing a liquid-absorbent core with a composite porous structure. The manufacturing method of the composite porous liquid-absorbing core has the advantages of simple process, controllable pore structure size and porosity, and controllable hydrophilic and hydrophobic properties of the surface of the liquid-absorbing core, and has the advantages of high capillary force, small gas-liquid flow resistance, and the like.

The manufacturing method of the composite porous structure liquid-absorbent core of the present invention comprises the following steps:

(1) Design a three-dimensional skeleton structure model; the model of the present invention is designed by three-dimensional software, and the model of this design is made of a millimeter macroporous skeleton structure inside a nested liquid-absorbing core, and the model is imported into a 3D printing system to control the printing process through slicing. followed by additive manufacturing;

(2) Import the designed three-dimensional skeleton structure model into the 3D printing system, use metal powder as the raw material, and use the laser sintering process to print, and control the laser power, scanning speed, scanning distance and powder layer thickness to obtain micron pores The porous skeleton structure of the liquid-absorbing core;

(3) After the printing is finished, inject oxygen into the printer cavity, and the oxygen content is 2%-16%;

(4) Perform laser printing on the surface of the porous skeleton of the liquid-absorbing core containing micron pores, adjust the power of the 3D printing laser to 5-100W, the scanning speed to 5-200mm/s, the laser pulse frequency to 10-100kHz, and the scanning distance to 0.01-0.1mm;

(5) Repeat step (4) 2 to 10 times to form an ordered micro-nano pore structure on the surface of the liquid-absorbent core, and realize a liquid-absorbent core with a composite porous structure manufactured with gradient pores and surface hydrophilicity and hydrophobicity controllable. Preferably, the particle size of the metal powder is 10-80 μm.

Preferably, the laser power is 140-2000W, the scanning speed is 2000-4000mm/s, and the thickness of the printed powder layer is 0.1-1mm.

Preferably, in the laser sintering process, the scanning rotation angle of the laser is 90°, the scanning distance is 0.1mm-1.2mm, the powder is laid layer by layer, and unidirectional cross-line scanning is performed.

Preferably, the size of the micro-nanopores in the liquid-absorbing core is 0.5-200 μm, and the porosity is controlled at 5%-90%.

Preferably, the overall thickness of the composite porous structure liquid-absorbent core is 0.1-6 mm.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The composite gradient structure of the liquid-absorbing core of the present invention is designed by three-dimensional software, and the porous liquid-absorbing core is directly printed into shape by 3D printing technology, and the size and porosity of the composite pore structure can be precisely controlled. Without mold development and additional processing, various forms of composite porous structures can be formed at one time, such as the development and manufacture of liquid-absorbing cores such as loop heat pipes, vapor chambers, and capillary pump loop heat pipes. In addition, the composite gradient porous structure realizes the composite of micro-nano-scale pores and millimeter-scale pores, which satisfies the excellent capillary performance of the liquid-absorbent core and reduces the resistance to gas-liquid flow.

(2) The liquid-absorbing core with composite porous structure of the present invention can also control the hydrophilicity and hydrophobicity of the liquid-absorbing core while forming the composite gradient pores at one time, realizing the one-time formation of gradient pores + interface control, without additional surface post-treatment process, the fabricated composite gradient porous liquid-absorbent core can realize enhanced heat transfer and zonal regulation of condensation.

Description of drawings

Fig. 1 is a three-dimensional model diagram of a liquid-absorbing core with a composite porous structure of the present invention.

Fig. 2 is the structure of the composite porous liquid-absorbent core whose framework contains micro-pores in Example 1 of the present invention.

Fig. 3 is the micro-pore structure inside the framework of the composite gradient porous liquid-absorbent core in Example 1 of the present invention.

Fig. 4 shows the surface topography and wettability measurement of the liquid-absorbent core with composite porous structure in Example 1 of the present invention.

Fig. 5 is the internal micro-pore structure of the liquid-absorbing skeleton of the composite porous structure in Example 2 of the present invention.

Fig. 6 is a comparison of the thermal resistance of the skeleton comprising a porous liquid-absorbing core and the liquid-absorbing core with a solid skeleton structure in Example 2 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with specific examples.

Example 1

A method for manufacturing a composite porous structure liquid-absorbing core, the specific steps are as follows:

Three-dimensional modeling software was used to construct the skeleton structure of the composite porous liquid-absorbing core. The designed wall thickness of the porous structure was 0.5 mm, the channel structure was designed as a rectangle, and the length and width of the channel structure were 1×0.5 mm. Figure 1 is a three-dimensional model diagram of a composite porous liquid-absorbent core manufactured by additive manufacturing.

The model is introduced into the 3D printing system and processed by slicing for additive manufacturing. The metal powder material used in this example is AlSi10Mg, and the particle size range of the powder is 10-60 μm.

Set the laser power for printing to 380W, the scanning speed to 3000mm/s, the thickness of the powder coating layer to 0.04mm, and the laser scanning distance to 0.1mm to ensure that the porous skeleton can have a good forming effect and make it have good mechanical strength .

The rotation angle of the 3D printer laser is controlled to 90°, and the scanning paths of the lasers intersect each other during the construction process, and the composite porous structure is formed by layer-by-layer line scanning.

The base plate of the 3D printing workbench is connected with the bottom plate of the heat pipe to be manufactured by silica gel or bolts. The laser scans the outline of the bottom plate. After the scanning is completed, the composite porous liquid-absorbing core structure is started on the bottom plate. Figure 2 and Figure 3 show the composite porous structure liquid-absorbent core with the skeleton containing micro-pores and the micro-pore structure inside the skeleton printed in this embodiment.

After the above-mentioned composite porous structure is printed, oxygen is introduced into the cavity of the 3D printing chamber to keep the oxygen content in the cavity at 8%.

Adjust the 3D printing laser power to 50W, the scanning speed to 80mm/s, the laser pulse frequency to 60kHz, and the scanning interval to 0.05mm, and perform post-printing treatment on the surface of the composite porous liquid-absorbing core.

Keeping the above laser parameters unchanged, repeat scanning the surface of the porous liquid-absorbing core structure 5 times to ensure that the surface of the liquid-absorbing core forms a uniform micro-nano pore structure, so as to control the surface of the composite porous liquid-absorbing core to exhibit hydrophilic characteristics, and the hydrophilic surface It can significantly enhance the heat transfer limit of the wick product. Figure 4 is the surface morphology and wettability measurements of the composite porous structure after surface printing, and the surface of the structure shows significant hydrophilicity.

After the printing of the composite porous structure absorbent core is completed, unscrew the bolts or heat to make the silica gel invalid and take off the printed absorbent core without subsequent machining such as wire cutting. Ultrasonic cleaning removes loose unmelted powder on the surface of the wick for subsequent use.

The internal pore characteristics of the skeleton of the composite porous liquid-absorbing core in the embodiment are measured by a mercury porosimeter, and the pore diameter is 80 μm, and the porosity is 25%.

Example 2

A method for manufacturing a composite porous structure liquid-absorbing core, the specific steps are as follows:

Three-dimensional modeling software is used to build a composite porous skeleton structure, and the size of the large pores in the liquid-absorbing core model is 0.5mm×1mm.

The model is sliced and then additively manufactured. The difference from Example 1 is that the metal powder material used in this example is 316L, and the powder particle size ranges from 20 to 60 μm.

Set the laser power for printing to 800W, the scanning speed to 3600mm/s, the thickness of the powder coating layer to 0.03mm, the laser scanning distance to 0.12mm, and control the laser rotation angle of the 3D printer to 60°, and the laser scanning path during the construction process Intersect each other and scan layer by layer to form a composite structure.

The base plate of the 3D printing workbench is connected with the bottom plate of the heat pipe to be manufactured by silica gel or bolts. The laser scans the outline of the bottom plate. After the scanning is completed, the composite porous liquid-absorbing core structure is started on the bottom plate. Fig. 5 is a composite porous skeleton structure containing micro-pores with a smaller size printed in Example 2.

After the above-mentioned composite porous structure is printed, oxygen is introduced into the cavity of the 3D printing chamber to keep the oxygen content in the cavity at 12%.

The 3D printing laser power was adjusted to 30W, the scanning speed was 60mm/s, the laser pulse frequency was 20kHz, and the scanning interval was 0.01mm, and the post-treatment of the surface of the 3D printing composite porous liquid-absorbing core was carried out.

Keeping the above laser parameters unchanged, repeat scanning the surface of the porous liquid-absorbing core structure 8 times to ensure that the surface of the liquid-absorbing core forms a uniform micro-nano pore structure.

After the composite porous structure absorbent core is printed, unscrew the bolts or heat to make the silica gel invalid and remove the printed absorbent core. Ultrasonic cleaning of loose unmelted powder on the surface of the wick for subsequent use.

The internal pore diameter and porosity of the skeleton of the composite porous liquid-absorbing core in the embodiment are measured by a mercury porosimeter to be 45 μm and 20%, respectively.

To further illustrate the advantages of the composite porous liquid-absorbing core structure in the embodiment in enhancing the heat transfer performance of the heat pipe, Figure 6 shows the millimeter/micron composite porous structure+hydrophilic surface manufactured by the process in Example 2 for loop suction Comparison of heat transfer resistance of liquid core. It can be seen from Figure 6 that the composite porous liquid-absorbent core containing micro-nano pores inside the skeleton controlled by surface hydrophilicity and hydrophobicity is significantly lower than the solid skeleton structure, and has a higher heat transfer heat load.

The present invention can manufacture composite porous liquid-absorbing cores of millimeter scale and micro-nano scale at one time without additional machining, and the design of the macropore structure in the liquid-absorbing core is flexible and various in form, while the micro-nano pore size and porosity structure can be obtained by process Design and controllable preparation of additive materials, freely design additive manufacturing process routes according to different pore structures, and realize rapid development and manufacture of composite porous liquid-absorbent cores. The controllable manufacture of the pore structure is realized by changing the process parameters, so the capillary performance can be significantly increased while the gas-liquid flow resistance can be reduced.

The size of the micro-nano pores formed according to the existing additive manufacturing method is 0.5-200 μm, and the porosity is 5-90%. It is controllable and overcomes the shortcomings of the existing composite liquid-absorbing core manufacturing.

The porous liquid-absorbing core manufactured in the present invention can control the surface wettability while constructing a composite gradient pore structure through laser parameter control. The hydrophilic surface increases the heat transfer limit of the wick, while the hydrophobic surface enhances condensation, resulting in a combined increase in the heat transfer efficiency of the heat pipe or vapor chamber.

It should be noted that the above examples are only a few specific embodiments of the present invention, and obviously the present invention is not limited to the above embodiments, and other modifications are also possible. All modifications directly derived or indirectly derived from the disclosure content of the present invention by those skilled in the art should be considered as the protection scope of the present invention.

Claims (5)

1. A method of making a composite porous structured wick, comprising the steps of:

(1) Designing a three-dimensional skeleton structure model;

(2) Introducing the designed three-dimensional skeleton structure model into a 3D printing system, printing by using metal powder as a raw material and adopting a laser sintering process, and obtaining the liquid absorption core skeleton structure containing the micropores by controlling laser power, scanning speed, scanning interval and powder spreading layer thickness;

(3) After printing, oxygen is introduced into the printer cavity, wherein the oxygen content is 2% -16%;

(4) Adjusting the laser parameters of a printer, and carrying out surface laser printing on the printed liquid absorption core skeleton structure containing the micro-pores;

(5) Repeating the step (4) for 2-10 times, and forming an ordered micro-nano pore structure on the surface of the liquid absorption core to control the hydrophilicity and hydrophobicity of the surface of the liquid absorption core with the composite porous structure;

in the step (4), the power of the 3D printing laser is 5-100W, the scanning speed is 5-200 mm/s, the laser pulse frequency is 10-100 kHz, and the scanning interval is 0.01-0.1 mm;

the laser power in the step (2) is 140-2000W, the scanning speed is 2000-4000 mm/s, and the thickness of the printing powder spreading layer is 0.03mm or 0.04mm.

2. A method of manufacturing a composite porous structured wick according to claim 1, characterized in that said metal powder is 10 to 80 μm.

3. A method of manufacturing a composite porous structured wick according to claim 1, characterized in that the laser sweep rotation angle in the laser sintering process is 90 °, the scanning pitch is 0.1mm to 1.2mm, the powder is laid layer by layer, and unidirectional cross-line scanning is performed.

4. A method of manufacturing a composite porous structured wick according to claim 1, characterized in that the micro-nano pore size in the composite porous structured wick is 0.5 to 200 μm and the porosity is controlled to be 5 to 90%.

5. A method of making a composite porous structured wick according to claim 1, characterized in that the composite porous structured wick has an overall thickness of from 0.1 to 6mm.

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