CN108251072B - A kind of preparation method of liquid metal composite phase change material - Google Patents

Abstract

A preparation method of a liquid metal composite phase change material belongs to the field of shaped composite phase change materials. First mix water-soluble metal salts, carbon nanotubes and PVDF raw materials in different proportions evenly, place them in a mold of a specific shape to dry, and finally dissolve the metal salts in hot water to obtain flexible carbon nanotubes of a specific shape. sponge. The prepared carbon nanotube sponge carrier material and liquid metal are placed in a vacuum environment at the same time by the melt impregnation method, the liquid metal core material is melted at an appropriate temperature, and the liquid metal is melted by the pores of the carbon nanotube sponge carrier material in the vacuum environment. The core material is adsorbed and confined in the pores, and then cooled to obtain a liquid metal composite phase change material. The invention can realize high-efficiency heat dissipation of CPU in different temperature ranges; controllable preparation of pore structure can be realized by changing the type and proportion of raw materials; the encapsulated shaped composite phase change material can solve the short circuit problem of electronic components caused by the free flow of liquid metal, and can also Satisfy the dynamic heat dissipation of flexible electronic components.

Description

A kind of preparation method of liquid metal composite phase change material

technical field

The invention belongs to the field of shaped composite phase change materials, in particular to a preparation method of a liquid metal composite phase change material.

Background technique

Electronic heat dissipation is related to the life and reliability of electronic equipment, and is a bottleneck affecting the development of today's electronic industry. With the development of the three major trends of high performance, miniaturization and integration in the electronics industry, the problem of heat dissipation is becoming more and more prominent. Especially for a chip with high thermal load sensitivity, the accumulation of heat at the chip will seriously affect its stability and service life. Studies have shown that if the operating temperature of a single electronic component is increased by 10 ° C, its reliability will be reduced by 50%; and the failure of CPU is mostly caused by overheating. If the large amount of heat generated by the CPU work is not dissipated to the external environment in time, it may cause a crash at light level, and may burn the chip in severe cases. With the continuous upgrading of CPU performance, its cooling technology has increased from air cooling, heat pipe cooling to water cooling, thermal grease cooling and other higher technologies, but it still cannot fully meet people's needs for chip cooling. The thermal conductivity of liquid metal breaks through the traditional thermal conductivity several times, which can make the heat dissipation efficiency more efficient.

Liquid metal usually refers to alloy functional materials that are liquid at room temperature, such as metals and their alloys with a melting point below 30 °C, and low melting point alloy materials that are liquid in the working temperature range of 40 °C-300 °C. Liquid metal has the characteristics of low melting point, high thermal conductivity/conductivity, stable properties, high temperature resistance, non-volatile, non-toxic and environmentally friendly. Its melting point, adhesion, fluidity, electrical conductivity, thermal conductivity, etc. can be adjusted according to different needs. technical parameter. Due to the requirements of ultra-small size, low power consumption, low noise and even high-quality experience, liquid metal is currently mainly used for high-end CPU heat dissipation. Although the liquid metal can fully fill the micro-voids of the thermal interface, greatly improve the heat conduction rate between the heating element and the heat dissipation interface, and make the heat dissipation efficiency higher, but because the liquid metal is in a liquid state during operation, it is easy to cause short circuit problems in electronic circuits, which will directly Affect the normal operation of the CPU, or even damage the CPU. Therefore, we used water-soluble metal salts as templates to synthesize shape-controllable flexible carbon nanotube sponges using carbon nanotubes and poly(vinylidene fluoride) (PVDF) for encapsulating liquid metals to prepare stereotyped composite phase transitions. Shape Stabilized Phase Change Materials (ss-PCMs), this method fixes the liquid metal inside the sponge pores, which can effectively solve the short circuit problem caused by the free flow of liquid metal. In addition, the carbon nanotube sponge has good flexibility and can be made into different shapes, which can meet the heat dissipation of dynamic flexible electronic components, so it has a wider application prospect for heat dissipation.

SUMMARY OF THE INVENTION

The purpose of the present invention is to prepare a flexible carbon nanotube sponge with a water-soluble metal salt as a template, carbon nanotubes and polyvinylidene fluoride as raw materials, and then use the pores to encapsulate the liquid metal phase change core material to prepare a new type of liquid metal composite phase change Therefore, a new type of liquid metal composite phase change material that is simplified, fast and green can be developed to improve the heat dissipation performance of the electronic component CPU. The prepared composite phase change material can effectively solve the circuit short circuit caused by the free flow of liquid metal. At the same time, the choice of liquid metal is diversified, which can meet the efficient heat dissipation of CPUs in different temperature ranges, and can also meet the heat dissipation of dynamic flexible electronic components.

Technical scheme of the present invention: 1) First, the water-soluble metal salts, carbon nanotubes and polyvinylidene fluoride raw materials in different proportions are mixed uniformly by the physical mixing method, placed in a mold of a specific shape, and then placed in an oven at 200-300 ° C After a certain period of time, a block material of a specific shape is obtained, and finally, it is placed in hot water to completely dissolve the metal salt in it to obtain a flexible carbon nanotube sponge of a specific shape. Among them, by adjusting the ratio of raw materials, flexible carbon nanotube sponges with different pore sizes can be obtained, so as to better match different types of liquid metal core materials; 2) Using the melt impregnation method, the prepared carbon nanotube sponge carrier material and liquid metal are simultaneously Put it in a vacuum environment, according to the type of liquid metal core material, select the appropriate temperature to melt it, use the pores of the carrier material to absorb and confine the liquid metal core material in the pores in a vacuum environment, and then cool to obtain a new type of liquid metal composite Phase change material.

The specific preparation steps are:

(1) Preparation of flexible carbon nanotube sponge carrier:

First, the water-soluble metal salts, carbon nanotubes and polyvinylidene fluoride raw materials are mixed uniformly, and then placed in a mold with a specific shape and placed in an oven at 200-300 ° C for 1-5 hours. Finally, the above product was washed in hot water at 50-90°C for several times to completely remove the water-soluble metal salt inside, and vacuum dried at 100-150°C for 12-36 hours to obtain a flexible carbon nanotube sponge carrier material with a specific shape. Wherein, the mass ratio of water-soluble metal salt: carbon nanotube: polyvinylidene fluoride: 1-10:1-100:1-10.

(2) Preparation of liquid metal composite phase change material:

The flexible carbon nanotube sponge carrier material prepared above was evacuated at 100° C. for 12-36 hours to completely open the internal pores. Then, the vacuum-treated carbon nanotube sponge carrier material and the liquid metal are placed in a vacuum flask at the same time. According to the type of the liquid metal core material, a suitable temperature is selected to melt it, and the liquid metal is melted by the pores of the carrier material in a vacuum environment. The core material is adsorbed and confined in the pores, and then cooled to obtain a new liquid metal composite phase change material. Wherein, the mass ratio of the liquid metal core material and the carbon nanotube sponge carrier is 1-100:1-100.

Further, the water-soluble metal salts include: sodium chloride, potassium chloride, magnesium chloride, calcium chloride, ammonium chloride, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium sulfate, potassium sulfate, One or more of sodium bisulfate, potassium bisulfate, etc.

Further, the liquid metal core material includes: Bi ₂₀ Pb ₂₀ Hg ₆₀ (20° C.), Bi ₄₅ Pb ₂₃ Sn ₈ Cd ₅ In ₁₉ (47° C.), Bi ₄₉ Pb ₁₈ Sn ₁₂ In ₂₁ (57° C.) , Bi ₅₀ Pb ₂₇ Sn ₁₃ Cd ₁₀ (70°C), Bi ₅₂ Pb ₄₀ Cd ₈ (92° C), Bi ₅₃ Pb ₃₂ Sn ₁₅ (96° C), Bi ₅₄ Pb ₂₆ Cd ₂₀ (103° C), Bi _55.5 Pb _44.5 (124℃), Bi ₅₆ Sn ₄₀ Zn ₄ (130℃), Bi ₂₉ Pb ₄₃ Sn ₂₈ (132℃), Bi ₅₇ Sn ₄₃ (138℃), Pb ₃₂ Sn ₅₀ Cd ₁₈ (145℃), Bi ₅₀ One or more of Pb ₅₀ (160°C), etc., where the subscript number represents the percentage of the component, and the temperature represents the melting point.

The advantages of the present invention are: 1) to develop a new type of liquid metal composite phase change material that is simplified, fast and green; 2) the selection of liquid metal is diversified, which can realize the efficient heat dissipation of the CPU in different temperature ranges; 3) the channel structure Adjustable, can effectively prevent the short circuit problem of electronic components caused by the free flow of liquid metal, and can also meet the heat dissipation of dynamic flexible electronic components.

Description of drawings

FIG. 1 is a flexible demonstration diagram of the carbon nanotube sponge obtained in Example 1 of the present invention.

FIG. 2 is the SEM of the carbon nanotube sponge obtained in Example 1 of the present invention.

FIG. 3 is a TEM of the carbon nanotube sponge obtained in Example 1 of the present invention.

FIG. 4 is the Raman of the carbon nanotube sponge obtained in Example 1 of the present invention.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

Implementation Case 1

(1) Preparation of flexible carbon nanotube sponge carrier material:

Mix 1g of polyvinylidene fluoride, 7g of sodium chloride and 0.2g of carbon nanotubes mechanically evenly, then add it to a cylindrical mold, place it in a 200°C oven for 4 hours, take out the product and immerse it in 90°C hot water to completely dissolve the inside. Sodium chloride, and finally dried in a vacuum oven at 100 °C for 24 h to obtain a cylindrical flexible carbon nanotube sponge carrier material. The flexibility demonstration is shown in Figure 1, SEM is shown in Figure 2, TEM is shown in Figure 3, and Raman is shown in Figure 4 shown.

(2) Preparation of liquid metal composite phase change material:

The flexible carbon nanotube sponge carrier material prepared above was evacuated at 100° C. for 24 hours to completely open the internal pores. Then, the vacuum-treated carbon nanotube sponge carrier material and the liquid metal Bi ₄₅ Pb ₂₃ Sn ₈ Cd ₅ In ₁₉ were placed in a vacuum flask at the same time, heated to 50 ° C to melt them, and the pores of the carrier material were used in a vacuum environment to melt them. The liquid metal Bi ₄₅ Pb ₂₃ Sn ₈ Cd ₅ In ₁₉ is adsorbed and confined in the pores, and then cooled to obtain a new liquid metal Bi ₄₅ Pb ₂₃ Sn ₈ Cd ₅ In ₁₉ composite phase change material.

Implementation case 2

(1) Preparation of flexible carbon nanotube sponge carrier material:

Mix 0.8g of polyvinylidene fluoride, 5g of sodium chloride and 0.3g of carbon nanotubes mechanically evenly, then add it to a square mold, place it in a 220°C oven for 2 hours, take out the product and immerse it in 80°C hot water to completely dissolve it. of sodium chloride, and finally dried in a vacuum oven at 120 °C for 18 h to obtain a square flexible carbon nanotube sponge carrier material.

(2) Preparation of liquid metal composite phase change material:

The flexible carbon nanotube sponge carrier material prepared above was evacuated at 100° C. for 18 hours to completely open the internal pores. Then, the vacuum-treated carbon nanotube sponge carrier material and the liquid metal Bi ₄₉ Pb ₁₈ Sn ₁₂ In ₂₁ were placed in a vacuum flask at the same time, heated to 60 ° C to melt it, and the liquid metal was melted by the pores of the carrier material in a vacuum environment. The adsorption of Bi ₄₉ Pb ₁₈ Sn ₁₂ In ₂₁ was confined in the pores, and then cooled to obtain a new liquid metal Bi ₄₉ Pb ₁₈ Sn ₁₂ In ₂₁ composite phase change material.

Implementation Case 3

(1) Preparation of flexible carbon nanotube sponge carrier material:

Mix 0.6g of polyvinylidene fluoride, 6g of sodium chloride and 0.5g of carbon nanotubes mechanically evenly, then add it to a rectangular mold, place it in a 240°C oven for 1 hour, take out the product and immerse it in 85°C hot water to dissolve completely The sodium chloride inside was finally dried in a vacuum oven at 140 °C for 20 h to obtain a rectangular flexible carbon nanotube sponge carrier material.

(2) Preparation of liquid metal composite phase change material:

The flexible carbon nanotube sponge carrier material prepared above was evacuated at 100° C. for 20 hours to completely open the internal pores. Then, the vacuum-treated carbon nanotube sponge carrier material and the liquid metal Bi ₅₀ Pb ₂₇ Sn ₁₃ Cd ₁₀ were placed in a vacuum flask at the same time, heated to 75 ° C to melt it, and the liquid metal was melted by the pores of the carrier material in a vacuum environment. The adsorption of Bi ₅₀ Pb ₂₇ Sn ₁₃ Cd ₁₀ was confined in the pores, and then cooled to obtain a new liquid metal Bi ₅₀ Pb ₂₇ Sn ₁₃ Cd ₁₀ composite phase change material.

Implementation Case 4

(1) Preparation of flexible carbon nanotube sponge carrier material:

Mix 0.5g of polyvinylidene fluoride, 10g of sodium chloride and 0.8g of carbon nanotubes mechanically evenly, then add it to a diamond-shaped mold, place it in a 250°C oven for 5 hours, take out the product and immerse it in 80°C hot water to completely dissolve it. of sodium chloride, and finally dried in a vacuum oven at 120 °C for 36 h to obtain a diamond-shaped flexible carbon nanotube sponge carrier material.

(2) Preparation of liquid metal composite phase change material:

The flexible carbon nanotube sponge carrier material prepared above was evacuated at 100° C. for 36 hours to completely open the internal pores. Then, the vacuum-treated carbon nanotube sponge carrier material and the liquid metal Bi ₅₂ Pb ₄₀ Cd ₈ were placed in a vacuum flask at the same time, heated to 95 ° C to melt it, and the liquid metal Bi ₅₂ was melted by the pores of the carrier material in a vacuum environment. The adsorption of Pb ₄₀ Cd ₈ is confined in the pores, and then cooled to obtain a new liquid metal Bi ₅₂ Pb ₄₀ Cd ₈ composite phase change material.

Claims (4)

1. A preparation method of a liquid metal composite phase-change material is characterized by comprising the following preparation steps:

1) firstly, uniformly mixing water-soluble metal salt, carbon nano tube and polyvinylidene fluoride raw materials in different proportions by adopting a physical mixing method, placing the mixture in a mould in a specific shape, then placing the mould in an oven at the temperature of 200-300 ℃ for a certain time to obtain a block material in a specific shape, and finally placing the block material in hot water to completely dissolve the metal salt in the block material so as to obtain flexible carbon nano tube sponge in a specific shape; the flexible carbon nanotube sponges with different apertures can be obtained by adjusting the proportion of the raw materials, so that different types of liquid metal core materials can be better matched;

2) and (2) simultaneously placing the prepared carbon nanotube sponge carrier material and liquid metal in a vacuum environment by adopting a melt impregnation method, selecting a proper temperature to melt the liquid metal core material according to the type of the liquid metal core material, adsorbing and limiting the liquid metal core material in the pore channel by utilizing the pore channel of the carrier material in the vacuum environment, and then cooling to obtain the liquid metal composite phase-change material.

2. The preparation method of the liquid metal composite phase-change material according to claim 1, which is characterized by comprising the following specific preparation steps:

(1) preparing a flexible carbon nanotube sponge carrier:

firstly, uniformly mixing water-soluble metal salt, a carbon nano tube and a polyvinylidene fluoride raw material, then placing the mixture in a mould with a specific shape, and placing the mould in an oven at 300 ℃ of 200-; finally, the product is placed in hot water at the temperature of 50-90 ℃ for washing for multiple times to completely remove the water-soluble metal salt in the product, and the product is dried in vacuum at the temperature of 100-150 ℃ for 12-36h to obtain the flexible carbon nanotube sponge carrier material with a specific shape; wherein, the water-soluble metal salt: carbon nanotube: the mass ratio of the polyvinylidene fluoride is as follows: 1-10:1-100: 1-10;

(2) preparing a liquid metal composite phase-change material:

vacuumizing the prepared flexible carbon nanotube sponge carrier material for 12-36h at 100 ℃, and completely opening the inner pore channel; then placing the carbon nanotube sponge carrier material subjected to vacuum treatment and liquid metal into a vacuum flask at the same time, selecting a proper temperature to melt the liquid metal core material according to the type of the liquid metal core material, adsorbing and limiting the liquid metal core material in a pore channel by utilizing the pore channel of the carrier material in a vacuum environment, and then cooling to obtain a liquid metal composite phase-change material; wherein the mass ratio of the liquid metal core material to the carbon nano tube sponge carrier is 1-100: 1-100.

3. The method for preparing a liquid metal composite phase change material according to claim 1 or 2, wherein the water-soluble metal salt comprises: one or more of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, ammonium chloride, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium sulfate, potassium sulfate, sodium bisulfate and potassium bisulfate.

4. The method for preparing a liquid metal composite phase change material according to claim 1 or 2, wherein the liquid metal core material comprises: bi₂₀Pb₂₀Hg₆₀Melting point of 20 ℃ and Bi₄₅Pb₂₃Sn₈Cd₅In₁₉Melting point of 47 ℃ and Bi₄₉Pb₁₈Sn₁₂In₂₁Melting point 57 ℃ and Bi₅₀Pb₂₇Sn₁₃Cd₁₀Melting point 70 ℃ and Bi₅₂Pb₄₀Cd₈Melting point of 92 ℃ and Bi₅₃Pb₃₂Sn₁₅Melting point of 96 ℃ and Bi₅₄Pb₂₆Cd₂₀Melting point of 103 ℃ and Bi_55.5Pb_44.5Melting point of 124 ℃ and Bi₅₆Sn₄₀Zn₄Melting point of 130 ℃ and Bi₂₉Pb₄₃Sn₂₈Melting point of 132 ℃ and Bi₅₇Sn₄₃Melting point of 138 ℃ and Pb₃₂Sn₅₀Cd₁₈Melting point of 145 ℃ and Bi₅₀Pb₅₀One or more of the melting points of 160 ℃ andthe middle subscript numbers represent the percent ingredients and the temperatures represent melting points.

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