Liquid metal composite with reduced surface tension and preparation method and application thereof

Abstract

The present invention discloses a liquid metal with reduced surface tension, a preparation method and application thereof. Liquid metal is mixed with thermal conductive powders such as boron nitride, graphene, and carbon fiber to obtain a liquid metal composite thermal conductive material with high thermal conductivity. The composition includes 75 to 96.5 parts of liquid metal, 0.5 to 5 parts of spherical tungsten particles, and 3 to 20 parts of thermal conductive powder in terms of mass fractions; wherein the metal tungsten nanoparticles play a role in reducing the surface tension of the liquid metal; after stirring and degassing, the liquid metal and the thermal conductive powder form a continuous thermal conductive path, and the viscosity of the composite material is greatly increased, reducing the risk of liquid metal leakage and short circuit and improving the stability of the liquid metal thermal conductive paste. The present invention successfully reduces the surface tension of the liquid metal by using metal tungsten nanoparticles, improves the wettability and affinity of the liquid metal with other thermal conductive powders, and can also be combined with other thermal conductive powders to expand the use of the liquid metal.

Description

Technical Field

[0001] The present invention relates to the field of thermal interface materials, and in particular to a liquid metal with reduced surface tension and a preparation method and application thereof, which can significantly reduce the surface tension of the liquid metal and improve the wettability to thermally conductive powders and solid surfaces, thereby improving the interface of the liquid metal composite thermal conductive paste, reducing the risk of short circuit of electronic equipment caused by liquid metal seepage, and improving the thermal conductivity of the composite thermal conductive paste, and can be applied to the fields of thermal interface materials and printed electronics. Background Art

[0002] The rapid development of science and technology has made electronic devices faster, smaller, and more power-dense. However, their heat generation is also increasing. Due to incomplete surface contact, there is always an air gap at the interface between the heat source and the heat sink. The thermal conductivity of air is only 0.026 W m -1 K -1 , hindering the effective heat transfer from the heat source to the heat sink. By applying thermal interface materials to fill the air gap, the contact resistance of the interface can be reduced and the thermal conductivity can be improved.

[0003] Gallium-based liquid metal has attracted great interest as a thermal interface material for thermal management due to its high thermal conductivity and flow state at room temperature. However, the surface tension of gallium is too high to wet the surface of heat source and heat sink, and direct application of liquid metal has great difficulties and risks, including device short circuit caused by liquid metal leakage.

[0004] Filling liquid metal with high thermal conductivity enhancing particles can not only further enhance thermal conductivity, but also reduce fluidity to reduce the risk of liquid metal leakage. However, the high surface tension of liquid metal also makes it difficult to bring liquid metal and thermal conductivity enhancing particles into good contact to prepare composite thermal interface materials.

[0005] Researchers are currently exploring the use of metal particles such as copper, iron, nickel, magnesium, silver, and tungsten as a second phase to reduce the surface tension of liquid metals. They can also be used as thermal conductivity enhancing particles to reduce leakage and increase the thermal conductivity of liquid metals. This technology has the following disadvantages: 1. Most of the metal particles currently reported will form intermetallic compounds, resulting in additional interfacial thermal resistance, which will lead to failure over time. 2. The mixing between metals also causes the conductivity to remain, causing short circuits in electronic devices. 3. Metal materials are bound to be used in large quantities as thermally conductive fillers, causing soaring costs, which is not conducive to large-scale industrial production. Therefore, it is necessary to develop a stable and low-cost method to reduce the surface tension of liquid metals, thereby laying the foundation for the development of liquid metal thermal conductive paste. Summary of the invention

[0006] The present invention solves the problems of difficulty in wetting solid thermal conductive powder on a low surface and leakage caused by high surface tension of liquid metal in the prior art by providing a liquid metal with reduced surface tension and a preparation method and application thereof.

[0007] In order to solve the above technical problems, the present invention provides a liquid metal with reduced surface tension, wherein the raw materials include, by weight, 75-96.5 parts of liquid metal, 0.5-5 parts of metal tungsten nanoparticles, and 3-20 parts of thermal conductive powder. The metal tungsten nanoparticles can reduce the surface tension of the liquid metal, thereby increasing the affinity between the liquid metal and the thermal conductive powder, and enhancing the thermal conductivity of the liquid metal composite material.

[0008] In a preferred embodiment of the present invention, the liquid metal is a liquid metal with a melting point of -40 to 60°C.

[0009] The liquid metal is metallic gallium or its alloy. Preferably, the liquid metal is selected from gallium-based alloys.

[0010] Furthermore, the liquid metal is selected from at least one of gallium-indium alloy and gallium-indium-tin alloy.

[0011] Wherein, the metal tungsten nanoparticles have a particle size of 10 to 100 nanometers, preferably 20 nanometers.

[0012] Wherein, the thermally conductive powder includes at least one of boron nitride, carbon fiber, graphene, aluminum oxide, aluminum nitride, zinc oxide, and silicon carbide.

[0013] In order to solve the above technical problems, the present invention also provides a method for preparing liquid metal with reduced surface tension, comprising the following steps:

[0014] First, the metal tungsten nanoparticles in the formula amount are stirred for the first time with liquid metal with high surface tension, and the liquid metal with surface tension reduced by nano-tungsten is stirred for the second time with thermal conductive powder to form a liquid metal composite embedded in the thermal conductive powder, and the composite is the high-performance liquid metal thermal conductive paste.

[0015] The stirring and mixing process conditions are: using a planetary stirring deaerator, a stirring speed of 1000 revolutions per minute, and a stirring time of 5 minutes.

[0016] The product obtained by the present invention is used as a heat conducting material.

[0017] The beneficial effects of the present invention are as follows: the present invention provides a liquid metal with reduced surface tension, a preparation method and an application thereof, which utilizes metal tungsten nanoparticles to form a micro / nano interface in a liquid metal matrix, thereby reducing the surface tension of the liquid metal, effectively improving the affinity between the liquid metal and the thermal conductive powder, increasing the thermal conductivity path and viscosity of the composite material, avoiding oil separation and liquid metal seepage, and the product is easy to store and has a prolonged shelf life. It exhibits a good thermal conductivity coefficient in a thermal conductivity performance test, thereby expanding the application scenarios of the liquid metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the contact angle between the liquid metal mixed with metal tungsten nanoparticles and the boron nitride pressed sheet described in Example 1 of the present invention;

[0019] Figure 2 is the contact angle between the liquid metal and the boron nitride pressed sheet described in Example 1 of the present invention;

[0020] Figure 3 This is a digital photo of the composite thermal conductive paste of liquid metal boron nitride mixed with metal tungsten nanoparticles as described in Example 1 of the present invention;

[0021] Figure 4 is a scanning electron microscope photograph of the composite thermal conductive paste of liquid metal boron nitride mixed with metal tungsten nanoparticles described in Example 1 of the present invention;

[0022] Figure 5 This is a digital photo of the powder prepared by mixing the liquid metal obtained in Comparative Example 1 with boron nitride. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0024] A liquid metal with reduced surface tension, comprising the following components in parts by weight:

[0025] 75 to 96.5 parts of liquid metal, wherein the liquid metal has a melting point of -40 to 60° C., preferably a liquid metal having a melting point of -40 to 30° C., including gallium-indium alloy, gallium-indium-tin alloy, etc.;

[0026] 0.5-5 parts of tungsten, wherein the tungsten is one of nanometer and micrometer, preferably nanometer spherical tungsten, specifically, the tungsten particle size is 10-100 nanometers rice .

[0027] 3 to 20 parts of thermally conductive powder, wherein the thermally conductive powder includes at least one of boron nitride, carbon fiber, and graphene; specifically, in order to obtain a higher thermal conductivity coefficient, the particle size of the thermally conductive powder is 5 to 50 microns.

[0028] The above-mentioned method for preparing liquid metal with reduced surface tension comprises the following steps:

[0029] First, add the liquid metal and nano-tungsten in the formula amount into the degassing mixing equipment, and stir and mix at a high speed of 1000 revolutions per minute for 5 minutes.

[0030] Then, the thermally conductive powder in the formula amount is added to the planetary degassing and mixing equipment. Under the same stirring conditions as above, the liquid metal whose surface tension is reduced by tungsten is fully infiltrated with the thermally conductive powder, and the powder is embedded in the liquid metal. The ratio of powder to liquid metal is controlled so that the composite material still has good fluidity.

[0031] Example 1

[0032] 0.1 g of particles with a diameter of 20 nanometers rice The metal tungsten nanoparticles and 9.3 g of liquid metal gallium indium tin alloy are put into a planetary stirring degassing machine at a mixing speed of 1000 revolutions per minute for a mixing time of 5 minutes to obtain liquid metal mixed with the metal tungsten nanoparticles.

[0033] In order to determine whether the liquid metal mixed with metal tungsten nanoparticles can improve the contact with the solid surface, a microinjector was used to drop liquid metal gallium indium tin alloy onto the surface of the boron nitride tablet, and the contact angle of the two was calculated using a static drop contact angle meter. The contact angle was recorded as 105°, such as Figure 1 shown.

[0034] Correspondingly, the contact angle between the liquid metal without metal tungsten nanoparticles and the boron nitride pressed sheet is 133°, as shown in Figure 2 , indicating that the contact between liquid metal and solid surface is significantly improved after mixing with metal tungsten nanoparticles.

[0035] Further, 0.6 g of 5 μm boron nitride was added to the liquid metal thermal conductive matrix with reduced surface tension, and the mixture was placed in a stirring cup and stirred in a planetary stirring degassing machine at a stirring speed of 1500 rpm for 10 minutes to obtain a liquid metal composite thermal conductive paste, as shown in the figure. Figure 4 shown.

[0036] The liquid metal boron nitride composite thermal conductive paste obtained by the above method was applied to a thermal conductivity meter to test its thermal conductivity. The test pressure was 50 N, the cold pole temperature was 20 °C, the hot pole temperature was 70 °C, and the thermal conductivity was 14.5 W m -1 K -1.

[0037] Example 2

[0038] 0.1 g of particles with a diameter of 20 nanometers rice The metal tungsten nanoparticles and 8.3 g of liquid metal gallium indium tin alloy are put into a planetary stirring degassing machine at a mixing speed of 1000 revolutions per minute for a mixing time of 5 minutes to obtain liquid metal mixed with the metal tungsten nanoparticles.

[0039] Furthermore, 1.6 g of graphene with a particle size of 10 μm was added to the liquid metal thermal conductive matrix with reduced surface tension, put into a stirring cup, and stirred in a planetary stirring degassing machine at a stirring speed of 2000 rpm for 15 minutes to obtain a liquid metal graphene composite thermal conductive paste.

[0040] The liquid metal composite thermal conductive paste obtained by the above method was applied to a thermal conductivity meter to test the thermal conductivity of the gray paste material. The test pressure was 50 N, the cold pole temperature was 20 °C, the hot pole temperature was 70 °C, and the thermal conductivity was 17.3 W m -1 K -1 .

[0041] Example 3

[0042] 0.1 g of metal tungsten nanoparticles with a particle size of 20 nanometers and 8.7 g of liquid metal gallium indium tin alloy were placed in a planetary stirring degassing machine at a mixing speed of 1000 rpm for 5 minutes to obtain liquid metal mixed with metal tungsten nanoparticles.

[0043] Furthermore, 1.2 grams of carbon fiber with a length of 50 microns was added to the above-mentioned liquid metal thermal conductive matrix with reduced surface tension, put into a stirring cup, and stirred in a planetary stirring degassing machine at a stirring speed of 1000 rpm for 10 minutes to obtain a liquid metal carbon fiber composite thermal conductive paste.

[0044] The liquid metal composite thermal conductive paste obtained by the above method was applied to a thermal conductivity meter to test the thermal conductivity of the gray paste material. The test pressure was 50 N, the cold pole temperature was 20 °C, the hot pole temperature was 70 °C, and the thermal conductivity was 23.8 W m -1 K -1 .

[0045] Comparative Example 1

[0046] 0.6 g of boron nitride with a particle size of 5 microns and 9.4 g of liquid metal gallium indium tin alloy were placed in a stirring cup, and the stirring speed was 1500 rpm for 5 minutes. No paste-like liquid metal boron nitride composite was obtained, and the product was black powder. Figure 5 shown.

[0047] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a liquid metal composite with reduced surface tension, wherein the components of the raw materials are as follows: 75-96.5 parts of liquid metal, 0.5-5 parts of metal tungsten nanoparticles, and 3-20 parts of thermal conductive powder; the melting point of the liquid metal is 10-60°C; It is characterized in that Firstly, the metal tungsten nanoparticles and liquid metal are mixed and stirred for the first time, and then the thermal conductive powder is added and mixed and stirred for the second time to form liquid metal embedded with the thermal conductive powder; The liquid metal is metallic gallium or its alloy; The thermally conductive powder includes at least one of boron nitride, carbon fiber, graphene, aluminum oxide, aluminum nitride, zinc oxide, and silicon carbide.

2. The method for preparing a liquid metal composite with reduced surface tension according to claim 1, characterized in that: The metal tungsten nanoparticles have a particle size of 10 to 100 nanometers.

3. The method for preparing a liquid metal composite with reduced surface tension according to claim 1, characterized in that: The raw materials are stirred and mixed using a planetary stirring and deaerator for high-speed mixing at a stirring speed of 500 to 2000 revolutions per minute for a stirring time of 3 to 20 minutes.

4. A liquid metal composite having reduced surface tension obtained by the preparation method according to any one of claims 1 to 3.

5. Use of a liquid metal composite with reduced surface tension as claimed in claim 4, characterized in that: As thermal conductive material.

Images