阅读说明：本技术 一种石墨烯-氮化硼纳米管导热填料的制备方法及取向性导热复合材料 (Preparation method of graphene-boron nitride nanotube heat-conducting filler and oriented heat-conducting composite material ) 是由 钱家盛 李旭 伍斌 杨斌 夏茹 曹明 于 2019-10-30 设计创作，主要内容包括：本发明公开一种石墨烯-氮化硼纳米管导热填料的制备方法及取向性导热复合材料,所述石墨烯-氮化硼纳米管导热填料的制备方法包括如下步骤：步骤S1,制备石墨烯水溶液；步骤S2,将尿素和硼酸加入所述石墨烯水溶液中反应,得到中间产物；步骤S3,将所述中间产物于保护气氛下煅烧,得到石墨烯-氮化硼纳米管导热填料。本发明制备的石墨烯-氮化硼纳米管导热填料中氮化硼纳米管是原位生长在石墨烯表面,且与石墨烯之间由C-N键共价相连,降低了石墨烯的界面热阻,提升了石墨烯的层间导热,将其作为填料掺杂至聚合物基体中,通过热压技术能够提高导热填料与聚合物基体的界面结合能力,减少界面处的声子散射,有效提高复合材料的导热性能。(The invention discloses a preparation method of a graphene-boron nitride nanotube heat-conducting filler and an oriented heat-conducting composite material, wherein the preparation method of the graphene-boron nitride nanotube heat-conducting filler comprises the following steps: step S1, preparing a graphene aqueous solution; step S2, adding urea and boric acid into the graphene aqueous solution for reaction to obtain an intermediate product; and step S3, calcining the intermediate product in a protective atmosphere to obtain the graphene-boron nitride nanotube heat-conducting filler. According to the graphene-boron nitride nanotube heat-conducting filler prepared by the invention, the boron nitride nanotube grows on the surface of the graphene in situ and is covalently connected with the graphene through a C-N bond, so that the interface thermal resistance of the graphene is reduced, the interlayer heat conduction of the graphene is improved, the graphene is doped into a polymer matrix as the filler, the interface bonding capability of the heat-conducting filler and the polymer matrix can be improved through a hot pressing technology, the phonon scattering at the interface is reduced, and the heat conducting property of a composite material is effectively improved.)

1. A preparation method of a graphene-boron nitride nanotube heat-conducting filler is characterized by comprising the following steps:

step S1, preparing a graphene aqueous solution;

step S2, adding urea and boric acid into the graphene aqueous solution for reaction to obtain an intermediate product;

and step S3, calcining the intermediate product in a protective atmosphere to obtain the graphene-boron nitride nanotube heat-conducting filler.

2. The method for preparing the graphene-boron nitride nanotube heat-conducting filler according to claim 1, wherein in step S3, the intermediate product is calcined in a protective atmosphere under the following conditions: the intermediate product is calcined for 3-7h at the temperature of 700-1000 ℃ under the protective atmosphere.

3. The method for preparing the graphene-boron nitride nanotube heat-conducting filler according to claim 1, wherein in step S3, the protective atmosphere is nitrogen or argon.

4. The method for preparing the graphene-boron nitride nanotube heat-conducting filler according to claim 1, wherein in step S1, the preparing the graphene aqueous solution specifically comprises: and (3) carrying out an electric stripping reaction on the graphite foil in the electrolyte, washing the obtained product, dispersing the product in water, and carrying out ice bath ultrasound to obtain the graphene aqueous solution.

5. The method for preparing the graphene-boron nitride nanotube thermal conductive filler according to claim 4, wherein the electrolyte comprises (NH)₄)₂SO₄Aqueous solution, NH₄Aqueous Cl solution and Na₂SO₄Aqueous solution, NaNO₃Aqueous solution, K₂SO₄Aqueous solution and NaClO₄Any one of the aqueous solutions, the electrolysisThe concentration of the solution is 0.1M-0.2M.

6. The method for preparing the graphene-boron nitride nanotube heat-conducting filler according to claim 4, wherein the mass ratio of the urea to the boric acid to the graphite foil used in the graphene aqueous solution is 35-45: 0.8-1.2: 0.1-0.3.

7. The method for preparing the graphene-boron nitride nanotube heat-conducting filler according to claim 1, wherein in step S2, the adding urea and boric acid into the graphene aqueous solution for reaction specifically includes: dissolving the urea in water, adding the boric acid, stirring at room temperature to obtain a mixed solution, adding the mixed solution into the graphene aqueous solution, stirring, centrifugally separating the obtained product, removing supernatant, and carrying out vacuum drying on the lower-layer substance to obtain the intermediate product.

8. The method for preparing the graphene-boron nitride nanotube heat-conducting filler according to claim 7, wherein the urea and the boric acid are stirred at room temperature for 10-14 hours, and the mixed solution and the graphene aqueous solution are stirred for 4-6 hours.

9. The preparation method of the oriented heat-conducting composite material is characterized by comprising the following steps of: the graphene-boron nitride nanotube heat-conducting filler obtained by the method for preparing the graphene-boron nitride nanotube heat-conducting filler according to any one of claims 1 to 8 is doped into a polymer solution, and is subjected to drying treatment and hot-pressing treatment to obtain the oriented heat-conducting composite material.

10. The method of claim 9, wherein the drying temperature for the drying treatment after the graphene-boron nitride nanotube heat-conducting filler is mixed with the polymer solution is 110-120 ℃, the hot-pressing temperature for the hot-pressing treatment is 200-220 ℃, and the hot-pressing pressure is 8-12 Mpa.

11. The method of claim 9, wherein the polymer used in the polymer solution comprises any one of polyvinylidene fluoride and epoxy resin.

12. An oriented thermal conductive composite comprising a graphene-boron nitride nanotube thermal conductive filler prepared by the method for preparing a graphene-boron nitride nanotube thermal conductive filler according to any one of claims 1 to 8 and a polymer matrix, or prepared by the method for preparing an oriented thermal conductive composite according to any one of claims 9 to 11; and the boron nitride in the graphene-boron nitride nanotube heat-conducting filler is connected with the graphene by a covalent bond.

Technical Field

The invention relates to the technical field of composite materials, in particular to a preparation method of a graphene-boron nitride nanotube heat-conducting filler and an oriented heat-conducting composite material.

Background

With the rapid development of electronic technology, electronic products undergo significant miniaturization and high power densification, and electronic devices integrate functions into small components. As the work efficiency of electronic products is higher and higher, the heat generated by electronic components is increased, and the temperature is increased dramatically. The high temperature not only affects the stability of the electronic product but also has a negative effect on the service life, and can cause equipment damage and even danger in severe cases. Therefore, the composite material with excellent heat conductivity is required to be used for timely conducting out the heat of the electronic product and maintaining the normal operation of the equipment. A common material used for heat dissipation of electronic devices is polymer, however, the low thermal conductivity of polymer limits its application to electronic devices that generate large amounts of heat. Therefore, how to improve the thermal conductivity of the polymer is critical.

In recent years, graphene heat conduction materials are widely concerned, graphene is a material with excellent heat conduction performance, but although graphene has good in-plane heat conduction, gaps exist between layers of graphene, interface heat resistance exists, interlayer heat transfer is hindered by the interface heat resistance, and the heat conduction coefficient in the vertical direction is extremely low. Improving the heat conductivity coefficient of graphene in the vertical direction by reducing the interface thermal resistance of graphene is a key point for applying graphene as a polymer heat-conducting filler. In the prior art, mechanical strain is applied to the thin graphene layer so as to reduce the interface thermal resistance, but the practical effect of the method is limited.

Disclosure of Invention

The invention solves the problem that the existing graphene interlayer has poor heat conduction effect.

In order to solve the above problems, the present invention provides a method for preparing a graphene-boron nitride nanotube thermal conductive filler, comprising the following steps:

step S1, preparing a graphene aqueous solution;

step S2, adding urea and boric acid into the graphene aqueous solution for reaction to obtain an intermediate product;

and step S3, calcining the intermediate product in a protective atmosphere to obtain the graphene-boron nitride nanotube heat-conducting filler.

Preferably, in step S3, the conditions for calcining the intermediate product under the protective atmosphere are: the intermediate product is calcined for 3-7h at the temperature of 700-1000 ℃ under the protective atmosphere.

Preferably, the protective atmosphere in step S3 is nitrogen or argon.

Preferably, the step S1 of "preparing the graphene aqueous solution" specifically includes: and carrying out an electric stripping reaction on the graphite foil in the electrolyte, washing the obtained product, dispersing the product in water, and carrying out ice bath ultrasonic treatment to obtain the graphene aqueous solution.

Preferably, the electrolyte comprises (NH)₄)₂SO₄Aqueous solution, NH₄Aqueous Cl solution and Na₂SO₄Aqueous solution, NaNO₃Aqueous solution, K₂SO₄Aqueous solution and NaClO₄And in any one of the aqueous solutions, the concentration of the electrolyte is 0.1M-0.2M.

Preferably, the mass ratio of the urea to the boric acid to the graphite foil used in the graphene aqueous solution is 35-45: 0.8-1.2: 0.1-0.3.

Preferably, the step S2 of "adding urea and boric acid into the graphene aqueous solution for reaction" specifically includes: dissolving the urea in water, adding the boric acid, stirring at room temperature to obtain a mixed solution, adding the mixed solution into the graphene aqueous solution, stirring, centrifugally separating the obtained product, removing supernatant, and carrying out vacuum drying on the lower-layer substance to obtain the intermediate product.

Preferably, the stirring time of the urea and the boric acid at room temperature is 10-14h, and the stirring time of the mixed solution and the graphene aqueous solution is 4-6 h.

The invention also provides a preparation method of the oriented heat-conducting composite material, which comprises the following steps:

the graphene-boron nitride nanotube heat-conducting filler obtained by the preparation method of the graphene-boron nitride nanotube heat-conducting filler is doped into a polymer solution, and the oriented heat-conducting composite material is obtained after drying treatment and hot pressing treatment.

Preferably, the drying temperature for the drying treatment after the graphene-boron nitride nanotube heat-conducting filler is mixed with the polymer solution is 110-.

Preferably, the polymer includes any one of polyvinylidene fluoride and epoxy resin.

The invention also provides an oriented heat-conducting composite material, which comprises the graphene-boron nitride nanotube heat-conducting filler prepared by the preparation method of the graphene-boron nitride nanotube heat-conducting filler and a polymer matrix, or is prepared by the preparation method of the oriented heat-conducting composite material; and the boron nitride in the graphene-boron nitride nanotube heat-conducting filler is connected with the graphene by a covalent bond.

Compared with the prior art, the invention has the beneficial effects that:

according to the graphene-boron nitride nanotube heat-conducting filler prepared by the invention, boron nitride grows on the surface of graphene in situ and is covalently connected with the graphene through a C-N bond, so that the interface thermal resistance of the graphene is reduced, the interlayer heat conduction of the graphene is improved, the graphene is doped into a polymer matrix as the filler, the interface bonding capability of the heat-conducting filler and the polymer matrix can be improved through a hot pressing technology, the phonon scattering at the interface is reduced, and the heat-conducting property of a composite material is effectively improved.

Drawings

FIG. 1 is a scanning electron microscope image of a graphene-boron nitride nanotube thermally conductive filler;

FIG. 2 is a scanning electron microscope image of graphene-boron nitride nanotube thermally conductive filler under different magnifications;

fig. 3 shows the thermal conductivity of the oriented thermal conductive composite material prepared with different contents of graphene-boron nitride nanotube thermal conductive filler.

Description of reference numerals:

1-boron nitride nanotubes.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

The embodiment of the invention provides a preparation method of a graphene-boron nitride nanotube heat-conducting filler, which comprises the following steps:

step S1, preparing a graphene aqueous solution;

step S2, adding urea and boric acid into the graphene aqueous solution for reaction to obtain an intermediate product;

and step S3, calcining the intermediate product in a protective atmosphere to obtain the graphene-boron nitride nanotube heat-conducting filler (EG-BN heat-conducting filler for short).

In the embodiment, the raw materials urea and boric acid for synthesizing boron nitride are mixed with the graphene aqueous solution and then calcined, and the generated boron nitride nanotube grows on the surface of graphene in situ and is connected with the graphene by a C-N bond, so that the graphene and the boron nitride nanotube are connected by a covalent bond, the interface thermal resistance of the graphene is reduced, and the interlayer heat conduction of the graphene is improved.

Preferably, the preparation of the graphene aqueous solution comprises the following steps:

and (3) carrying out an electric stripping reaction on the graphite foil in an electrolyte at normal temperature and normal pressure and under a constant voltage of 8-20V, dispersing the graphite foil in water after washing, and carrying out ice bath ultrasound to obtain the graphene aqueous solution. Wherein the electrolyte comprisesAmmonium sulfate ((NH)₄)₂SO₄) Aqueous solution, ammonium chloride (NH)₄Cl) aqueous solution, sodium sulfate (Na)₂SO₄) Aqueous solution, sodium nitrate (NaNO)₃) Aqueous solution, potassium sulfate (K)₂SO₄) Aqueous solution and sodium hypochlorite (NaClO)₄) In any of the aqueous solutions, the electrolyte concentration is between 0.1M and 0.2M, and in this embodiment, the electrolyte concentration is preferably 0.1M (NH)₄)₂SO₄An aqueous solution.

Step S2 specifically includes: dissolving urea in water, adding boric acid, stirring at room temperature to obtain a mixed solution, adding the mixed solution into a graphene aqueous solution, stirring, centrifugally separating the obtained product to remove supernatant, and carrying out vacuum drying on the obtained product to obtain an intermediate product.

Wherein the mass ratio of urea to boric acid to graphite foil is 35-45: 0.8-1.2: 0.1-0.3, mixing and stirring the urea and the boric acid for 10-14h, stirring the mixed solution of the urea and the boric acid and the graphene aqueous solution for 4-6h, and carrying out vacuum drying on the lower-layer substance obtained by centrifugal separation at the temperature of 60-80 ℃.

In step S3, the protective atmosphere is nitrogen or argon, and the calcination condition is 700-1000 ℃ for calcination for 3-7 h.

Scanning electron microscope tests are carried out on the prepared graphene-boron nitride nanotube heat conduction material, and the results are shown in fig. 1 and 2, so that the boron nitride nanotube vertically grows on the surface of the graphene, the boron nitride with a tubular structure can be clearly distinguished from fig. 2, and the inner diameter of the tube of the boron nitride nanotube is about 60 nanometers. According to the EG-BN heat-conducting filler prepared by the preparation method, the boron nitride nanotubes are connected to the graphene through covalent bonds, the method is different from a simple interlayer stacking mode between the graphene and the boron nitride nanotubes in the prior art, the interfacial resistance between graphene layers is reduced through the covalent bond combination mode, the heat-conducting capacity between the graphene layers is improved, and the heat-conducting filler has good heat-conducting performance.

The invention also provides an oriented heat-conducting composite material, which is prepared by doping the EG-BN heat-conducting filler obtained by the preparation method into a polymer solution, drying and hot-pressing. The polymer used in the polymer solution comprises any one of polyvinylidene fluoride and epoxy resin, the solvent used for dissolving the polymer comprises but is not limited to N, N-Dimethylformamide (DMF), the drying temperature for drying after the EG-BN heat-conducting filler is mixed with the polymer solution is 110-120 ℃, the hot-pressing temperature for hot-pressing is 200-220 ℃, and the hot-pressing pressure is 8-12 MPa.

Compared with the method for doping the graphene filler in the polymer, the EG-BN heat-conducting filler prepared by the embodiment is doped in the polymer, so that the interface bonding capability of the heat-conducting filler and a polymer matrix can be improved, the phonon scattering at the interface is reduced, and the heat conduction efficiency of the composite material is further improved. The heat conductivity coefficient of the oriented heat-conducting composite material prepared by the embodiment is measured to be 0.35-1.4W/(mK).

The present invention will be described in detail with reference to the following embodiments.