SiCw-C-CNT / ANF heat conduction composite material and preparation method thereof

Abstract

The invention discloses a SiCw-C-CNT / ANF heat conduction composite material and a preparation method thereof.The preparation method comprises the steps that ZIF-67 crystals grow on the surfaces of silicon carbide whiskers (SiCw) coated with dopamine (PDA), after high-temperature heat treatment, dopamine and ZIF-67 on the surfaces of the SiCw are converted into graphene-like carbonized dopamine and carbon nanotubes (CNT) respectively, and SiCw-C-CNT hybrid filler is obtained; and shearing and uniformly mixing the filler and aramid nanofiber (ANF) at a high speed, and carrying out vacuum filtration to obtain the SiCw-C-CNT / ANF heat-conducting composite material. According to the method disclosed by the invention, the contact thermal resistance between SiCw fillers can be remarkably reduced, so that the heat-conducting property of the polymer composite material is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of silicon carbide whisker / ANF composite materials, and in particular to a SiCw@C@CNT / ANF thermal conductive composite material and a preparation method thereof. Background Art

[0002] In recent years, the microelectronics industry, aerospace, electrical power and other fields have developed rapidly, and unprecedented demands have been placed on the integration and power of electronic components. With the high integration and high power of devices, local overheating has seriously reduced the service life and product performance of electronic equipment. Therefore, there is an urgent need for thermal management materials with excellent heat dissipation performance to solve this problem. Polymer materials are electrically insulating, lightweight, cheap and easy to obtain, which has led people to consider the possibility of using them as thermal management materials. However, the thermal conductivity of the polymer itself (0.1~0.3W·m -1 ·K -1 ) is extremely low and the thermal stability is also poor, which hinders their development in the field of thermal conductivity. The thermal conductivity of polymers is usually enhanced by introducing various thermal conductive fillers. Silicon carbide whiskers (SiCw) are widely used in thermally conductive polymer composites due to their high thermal conductivity, low thermal expansion coefficient, high melting point, excellent mechanical properties and high chemical stability. However, since silicon carbide whiskers are easy to agglomerate, it is impossible to construct a long-range orderly heat transfer path, and the existence of interfacial thermal resistance between silicon carbide whiskers will also affect the thermal conductivity of the composite material. Summary of the invention

[0003] Based on the above problems existing in the prior art, the present invention provides a SiCw@C@CNT / ANF thermal conductive composite material and a preparation method thereof, wherein SiCw@C@CNT hybrid filler is prepared by in situ growing carbon nanotubes on the surface of silicon carbide whiskers coated with carbonized dopamine, and then a layered structure is constructed with ANF through vacuum filtration to significantly improve the thermal conductivity of the composite material.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A preparation method of a SiCw@C@CNT / ANF thermal conductive composite material, characterized in that: dopamine (PDA) is first coated on the surface of a silicon carbide whisker (SiCw), and then ZIF-67 is uniformly loaded on the surface of the dopamine-coated silicon carbide whisker through the adsorption of catechol and amino groups in dopamine on cations, and then dopamine and ZIF-67 are respectively converted into graphene-like carbonized dopamine and carbon nanotubes (CNT) by high-temperature heat treatment to obtain a silicon carbide whisker hybrid filler loaded with carbonized dopamine and carbon nanotubes on the surface, which is recorded as SiCw@C@CNT; finally, the filler is uniformly sheared and mixed with aramid nanofibers (ANF) at high speed, and then the SiCw@C@CNT / ANF composite material is obtained by vacuum filtration. Specifically comprising the following steps:

[0006] Step 1: Preparation of SiCw@PDA

[0007] 0.5-1 g of silicon carbide whiskers were added into 100-200 mL of distilled water and ultrasonically dispersed uniformly; 0.5-1.0 g of dopamine hydrochloride was dissolved in 50-100 mL of 0.01 M Tris-HCl solution and then added into the silicon carbide whisker suspension, the pH was adjusted to 8-9, and stirred at 25° C. for 12-24 h; the product was separated by filtration and washed to neutrality, and vacuum dried at 60° C. to obtain dopamine-coated silicon carbide whiskers, which were recorded as SiCw@PDA.

[0008] Step 2: Preparation of SiCw@PDA@ZIF-67

[0009] 0.01-0.02 g of SiCw@PDA obtained in step 1 was added to 20-40 mL of methanol and ultrasonically dispersed evenly. 20-40 mL of a methanol solution containing 0.291-0.582 g of cobalt nitrate hexahydrate and 0.5-1 g of polyvinyl pyrrolidone was added dropwise and stirred evenly. Then 20-40 mL of a methanol solution containing 0.657-1.314 g of 2-methylimidazole was added dropwise and stirred for 3 h. The product was separated by suction filtration, washed and dried to obtain dopamine-coated silicon carbide whiskers with ZIF-67 crystals loaded on the surface, which were recorded as SiCw@PDA@ZIF-67.

[0010] Step 3: Preparation of SiCw@C@CNT

[0011] 0.1-0.2 g of SiCw@PDA@ZIF-67 obtained in step 2 is placed in a tube furnace, 1-2 g of dicyandiamide is added, and high-temperature heat treatment is performed under an argon atmosphere to convert dopamine and ZIF-67 crystals into carbonized dopamine and carbon nanotubes, respectively, to obtain SiCw@C@CNT filler.

[0012] Step 4: Preparation of SiCw@C@CNT / ANF

[0013] 0.04-0.4 g PPTA fiber and 0.06-0.6 g KOH are added to a mixture of 0.8-3.2 mL H2O and 40-80 mL DMSO, and the mixture is stirred evenly by magnetic force to obtain an ANF dispersion. The SiCw@C@CNT filler obtained in step 3 is added to the ANF dispersion and subjected to ultrasonic treatment. The obtained mixture is dropped into water, SiCw@C@CNT / ANF is precipitated by mechanical stirring, and the product is separated by suction filtration. 50-100 mg SiCw@C@CNT / ANF is added to 100-150 mL H2O, and the mixture is dispersed evenly by a homogenizer to obtain a SiCw@C@CNT / ANF aqueous suspension. Finally, the SiCw@C@CNT / ANF aqueous suspension is filtered through a polytetrafluoroethylene membrane to obtain a SiCw@C@CNT / ANF thermal conductive composite film.

[0014] Preferably, in step 3, the high temperature heat treatment is performed by heating the temperature to 1200-1350° C. and maintaining the temperature for 2-6 hours.

[0015] Preferably, in step 4, the mass fraction of SiCw@C@CNT / ANF filler in the composite material is 10-40wt%.

[0016] Preferably, in step 4, the pore size of the polytetrafluoroethylene membrane is 0.22 μm and the diameter is 47 mm.

[0017] The beneficial effects of the present invention are embodied in:

[0018] The present invention prepares SiCw@C@CNT hybrid filler by in-situ growing carbon nanotubes on the surface of carbonized dopamine-coated silicon carbide whiskers. The carbonized dopamine and carbon nanotubes on the surface of the silicon carbide whiskers can effectively reduce the contact thermal resistance between fillers and inhibit the agglomeration of silicon carbide whiskers. The layered structure is constructed by vacuum filtration self-assembly and ANF, thereby significantly improving the thermal conductivity of the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a SEM image of SiCw in Example 1 of the present invention;

[0020] Figure 2 This is a SEM image of SiCw@PDA obtained in Example 1 of the present invention;

[0021] Figure 3 This is a SEM image of SiCw@PDA@ZIF-67 obtained in Example 1 of the present invention;

[0022] Figure 4 This is a SEM image of SiCw@C@CNT obtained in Example 1 of the present invention;

[0023] Figure 5This is a cross-sectional SEM image of SiCw@C@CNT / ANF obtained in Example 1 of the present invention;

[0024] Figure 6 It is a comparison chart of thermal diffusion coefficients of samples obtained in Examples 1, 2, 3, 4 of the present invention and Comparative Examples 1, 2, 3, 4. DETAILED DESCRIPTION

[0025] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0026] Example 1

[0027] Step 1: Preparation of SiCw@PDA

[0028] 0.5g of silicon carbide whiskers were added to 200mL of distilled water and dispersed uniformly by ultrasonication. 0.5g of dopamine hydrochloride was dissolved in 50mL of 0.01M Tris-HCl solution, and then added to the silicon carbide whisker suspension, and the pH was adjusted to 8.5 with 1mol / L NaOH solution, and stirred at 25°C for 12h. The product was separated by filtration and washed to neutrality, and dried under vacuum at 60°C to obtain dopamine-coated silicon carbide whiskers, which were recorded as SiCw@PDA.

[0029] Step 2: Preparation of SiCw@PDA@ZIF-67

[0030] 0.02 g of SiCw@PDA obtained in step 1 was added to 40 mL of methanol and ultrasonically dispersed evenly. 20 mL of a methanol solution containing 0.437 g of cobalt nitrate hexahydrate and 0.5 g of polyvinyl pyrrolidone was added dropwise and stirred evenly. Then 20 mL of a methanol solution containing 0.986 g of 2-methylimidazole was added dropwise and stirred for 3 h. The product was separated by suction filtration and washed and dried to obtain dopamine-coated silicon carbide whiskers with ZIF-67 crystals loaded on the surface, which were recorded as SiCw@PDA@ZIF-67.

[0031] Step 3: Preparation of SiCw@C@CNT

[0032] 0.2 g of SiCw@PDA@ZIF-67 obtained in step 2 was placed in a tube furnace, 1 g of dicyandiamide was added, and the mixture was kept at 1200°C for 2 h under an argon atmosphere to convert dopamine and ZIF-67 crystals into carbonized dopamine and carbon nanotubes, respectively, to obtain SiCw@C@CNT filler.

[0033] Step 4: Preparation of SiCw@C@CNT / ANF

[0034] 0.2 g of PPTA fiber and 0.3 g of KOH were added to a mixture of 1.6 mL of H2O and 40 mL of DMSO, and magnetic stirring was performed to obtain a 5 mg / mL LANF dispersion. 5.6 mg SiCw@C@CNT filler was added to 10 mL ANF dispersion and homogenized by ultrasound; the resulting mixture was dropped into water, SiCw@C@CNT / ANF was precipitated by mechanical stirring at 200 rpm, and the product was separated by filtration; 50 mg SiCw@C@CNT / ANF was added to 100 mL H2O and dispersed evenly with a homogenizer to obtain a SiCw@C@CNT / ANF aqueous suspension; finally, the SiCw@C@CNT / ANF aqueous suspension was filtered with a polytetrafluoroethylene membrane (pore size 0.22 μm, diameter 47 mm) to obtain a SiCw@C@CNT / ANF composite film, in which the mass fraction of SiCw@C@CNT filler in the composite material was 10%.

[0035] Figure 1 is the SEM image of the silicon carbide whisker used in Example 1, Figure 2 This is the SEM image of SiCw@PDA obtained in Example 1. It can be seen that the PDA particles are evenly coated on the SiCw surface. Figure 3 This is the SEM image of SiCw@PDA@ZiF-67 obtained in Example 1. It can be seen that the ZiF-67 crystals are uniformly loaded on the dopamine-wrapped silicon carbide whiskers. Figure 4 This is the SEM image of SiCw@C@CNT obtained in Example 1. It can be seen that after high-temperature heat treatment, carbon nanotubes are successfully grown in situ on the surface of silicon carbide whiskers. Figure 5 This is the cross-sectional SEM image of the SiCw@C@CNT / ANF composite material obtained in Example 1. It can be seen that the composite material has a good layered structure, and the silicon carbide whiskers grown with carbon nanotubes are uniformly dispersed in the ANF matrix, which inhibits filler agglomeration and improves the thermal conductivity of the composite material.

[0036] Example 2

[0037] In this example, the SiCw@C@CNT / ANF composite material was prepared in the same manner as in Example 1, with the only difference being that in step 4, the amount of SiCw@C@CNT filler was 12.5 mg, and the mass fraction of SiCw@C@CNT filler in the obtained composite material was 20 wt %.

[0038] Example 3

[0039] In this example, the SiCw@C@CNT / ANF composite material was prepared in the same manner as in Example 1, with the only difference being that in step 4, the amount of SiCw@C@CNT filler was 21.4 mg, and the mass fraction of SiCw@C@CNT filler in the obtained composite material was 30 wt%.

[0040] Example 4

[0041] In this example, the SiCw@C@CNT / ANF composite material was prepared in the same manner as in Example 1, with the only difference being that in step 4, the amount of SiCw@C@CNT filler was 33.3 mg, and the mass fraction of SiCw@C@CNT filler in the obtained composite material was 40 wt%.

[0042] Comparative Example 1

[0043] This comparative example prepared the SiCw / ANF composite material according to the following steps:

[0044] 0.2g PPTA fiber and 0.3g KOH were added to a mixture of 1.6mL H2O and 40mL DMSO, and magnetic stirring was performed uniformly (stirring speed 200rpm, stirring time 72 hours) to obtain a 5mg / mL ANF dispersion. 5.6mg SiCw filler was added to 10mL ANF dispersion by ultrasonic homogenization; the resulting mixture was dropped into water, SiCw / ANF was precipitated by mechanical stirring at 200rpm, and the product was separated by suction filtration; 50mg SiCw / ANF was added to 100mL H2O and dispersed uniformly with a homogenizer to obtain a SiCw / ANF water suspension; finally, the SiCw / ANF water suspension was filtered with a polytetrafluoroethylene membrane (pore size 0.22μm, diameter 47mm) to obtain a SiCw / ANF composite film, in which the mass fraction of SiCw filler in the composite material was 10%.

[0045] Comparative Example 2

[0046] In this comparative example, a SiCw / ANF composite material was prepared in the same manner as in Comparative Example 1, except that the amount of SiCw filler used was 12.5 mg, and the mass fraction of SiCw filler in the obtained composite material was 20 wt %.

[0047] Comparative Example 3

[0048] In this comparative example, a SiCw / ANF composite material was prepared in the same manner as in Comparative Example 1, except that the amount of SiCw filler used was 21.4 mg, and the mass fraction of SiCw filler in the obtained composite material was 30 wt %.

[0049] Comparative Example 4

[0050] In this comparative example, a SiCw / ANF composite material was prepared in the same manner as in Comparative Example 1, except that the amount of SiCw filler used was 33.3 mg, and the mass fraction of SiCw filler in the obtained composite material was 40 wt %.

[0051] The thermal conductivity of the samples obtained in Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3, 4 is shown in Tables 1 and Figure 6 shown.

[0052] Table 1. Thermal diffusivity of samples obtained in various embodiments and comparative examples

[0053]

[0054] From Table 1 and Figure 6 It can be seen that the thermal diffusion coefficients of the samples obtained in Examples 1 to 4 are significantly improved compared with Comparative Examples 1 to 4. By comparison, it can be seen that the thermal diffusion coefficients of the silicon carbide whiskers loaded with carbonized dopamine and carbon nanotubes on the surface are significantly improved compared with the pure silicon carbide whiskers at the same filler content, and as the filler content increases, the thermal diffusion coefficient of the composite material shows an increasing trend, mainly because the in-situ growth of carbon nanotubes on the surface of the silicon carbide whiskers can effectively reduce the contact thermal resistance between the fillers, thereby improving the thermal conductivity.

[0055] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a SiCw@C@CNT / ANF thermally conductive composite material, Features: Dopamine is first coated on the surface of silicon carbide whiskers SiCw, and then ZIF-67 is evenly loaded on the surface of the dopamine-coated silicon carbide whiskers through the adsorption of catechol and amino groups in dopamine on cations. Dopamine and ZIF-67 are then converted into graphene-like carbonized dopamine and carbon nanotubes CNT, respectively, through high-temperature heat treatment to obtain a silicon carbide whisker hybrid filler with carbonized dopamine and carbon nanotubes loaded on the surface, which is recorded as SiCw@C@CNT. Finally, the filler and aramid nanofibers ANF are shear-mixed and evenly mixed, and then the SiCw@C@CNT / ANF thermal conductive composite material is obtained by vacuum filtration.

2. The preparation method according to claim 1, It is characterized in that The steps include: Step 1: Preparation of SiCw@PDA 0.5-1 g of silicon carbide whiskers were added to 100-200 mL of distilled water and ultrasonically dispersed uniformly; 0.5-1.0 g of dopamine hydrochloride was dissolved in 50-100 mL of 0.01 M Tris-HCl solution, and then added to the silicon carbide whisker suspension, the pH was adjusted to 8-9, and stirred at 25°C for 12-24 hours; The product was separated by filtration and washed to neutrality, and then dried in vacuum at 60°C to obtain dopamine-coated silicon carbide whiskers, which were denoted as SiCw@PDA. Step 2: Preparation of SiCw@PDA@ZIF-67 0.01-0.02 g of SiCw@PDA obtained in step 1 was added to 20-40 mL of methanol for uniform ultrasonic dispersion, 20-40 mL of a methanol solution containing 0.291-0.582 g of cobalt nitrate hexahydrate and 0.5-1 g of polyvinyl pyrrolidone was added dropwise and stirred evenly, and then 20-40 mL of a methanol solution containing 0.657-1.314 g of 2-methylimidazole was added dropwise, stirred for 3 h, and the product was separated by suction filtration. After washing and drying, dopamine-coated silicon carbide whiskers with ZIF-67 crystals loaded on the surface were obtained, which were recorded as SiCw@PDA@ZIF-67; Step 3: Preparation of SiCw@C@CNT 0.1-0.2 g of SiCw@PDA@ZIF-67 obtained in step 2 is placed in a tube furnace, 1-2 g of dicyandiamide is added, and high-temperature heat treatment is performed under an argon atmosphere to convert dopamine and ZIF-67 crystals into carbonized dopamine and carbon nanotubes, respectively, to obtain SiCw@C@CNT filler; Step 4: Preparation of SiCw@C@CNT / ANF Add 0.04-0.4 g PPTA fiber and 0.06-0.6 g KOH to 0.8-3.2 mL H 2 O and 40-80 mL DMSO were mixed and magnetically stirred to obtain ANF dispersion; the SiCw@C@CNT filler obtained in step 3 was added to the ANF dispersion and ultrasonically treated; the obtained mixture was dropped into water, SiCw@C@CNT / ANF was precipitated by mechanical stirring, and the product was separated by filtration; 50-100 mg SiCw@C@CNT / ANF was added to 100-150 mL H 2 O, and dispersed evenly with a homogenizer to obtain a SiCw@C@CNT / ANF water suspension; finally, the SiCw@C@CNT / ANF water suspension was filtered with a polytetrafluoroethylene membrane to obtain a SiCw@C@CNT / ANF thermal conductive composite film.

3. The preparation method according to claim 2, Features: In step 3, the high temperature heat treatment is to raise the temperature to 1200-1350° C. and keep it for 2-6 hours.

4. The preparation method according to claim 2, Features: In step 4, the mass fraction of SiCw@C@CNT / ANF filler in the composite material is 10-40wt%.

5. The preparation method according to claim 2, Features: In step 4, the pore size of the polytetrafluoroethylene membrane is 0.22 μm and the diameter is 47 mm.

6. A SiCw@C@CNT / ANF thermally conductive composite material obtained by the preparation method according to any one of claims 1 to 5.

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