A SiCw@C@CNT / ANF thermally conductive composite material and its preparation method

Abstract

This invention discloses a SiCw@C@CNT / ANF thermally conductive composite material and its preparation method. The method involves growing ZIF-67 crystals on the surface of dopamine (PDA)-coated silicon carbide whiskers (SiCw). After high-temperature heat treatment, the dopamine and ZIF-67 on the SiCw surface are converted into graphene-like dopamine carbide and carbon nanotubes (CNTs), respectively, to obtain a SiCw@C@CNT hybrid filler. The filler is then mixed uniformly with aramid nanofibers (ANF) under high-speed shearing, and the SiCw@C@CNT / ANF thermally conductive composite material is obtained by vacuum filtration. This method significantly reduces the contact thermal resistance between SiCw fillers, thereby significantly improving the thermal conductivity of the polymer composite material.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide whisker / ANF composite material technology, specifically to a SiCw@C@CNT / ANF thermally conductive composite material and its preparation method. Background Technology

[0002] In recent years, the rapid development of industries such as microelectronics, aerospace, and electrical power has placed unprecedented demands on the integration and power of electronic components. With the increasing integration and power of devices, localized overheating has severely reduced the lifespan and performance of electronic equipment. Therefore, there is an urgent need for thermal management materials with excellent heat dissipation properties to solve this problem. Polymer materials, due to their electrical insulation, lightweight, and readily available low cost, have led to consideration of their potential application as thermal management materials. However, the thermal conductivity of polymers themselves (0.1–0.3 W·m) is limited. -1 ·K -1 Their extremely low thermal conductivity and poor thermal stability hinder their development in the field of thermal conductivity. Enhancing the thermal conductivity of polymers is usually achieved by introducing various thermally conductive fillers. Silicon carbide whiskers (SiCw) are widely used in thermally conductive polymer composites due to their high thermal conductivity, low coefficient of thermal expansion, high melting point, excellent mechanical properties, and high chemical stability. However, because silicon carbide whiskers are prone to agglomeration, they cannot form long-range ordered heat transfer paths, and the interfacial thermal resistance between silicon carbide whiskers also affects the thermal conductivity of the composite material. Summary of the Invention

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

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for preparing a SiCw@C@CNT / ANF thermally conductive composite material is characterized by: first coating the surface of silicon carbide whiskers (SiCw) with dopamine (PDA); then, through the adsorption of cations by catechol and amino groups in dopamine, ZIF-67 is uniformly loaded onto the surface of the dopamine-coated silicon carbide whiskers; followed by high-temperature heat treatment to convert dopamine and ZIF-67 into graphene-like dopamine carbide and carbon nanotubes (CNTs), respectively, resulting in a silicon carbide whisker hybrid filler with surface-loaded dopamine carbide and carbon nanotubes, denoted as SiCw@C@CNT; finally, the filler is mixed uniformly with aramid nanofibers (ANF) under high-speed shearing and then vacuum filtered to obtain the SiCw@C@CNT / ANF composite material. The specific steps include the following:

[0006] Step 1: Preparation of SiCw@PDA

[0007] 0.5–1 g of silicon carbide whiskers were added to 100–200 mL of distilled water and ultrasonically dispersed until uniform. 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 the mixture was stirred at 25 °C for 12–24 h. The product was separated by filtration and washed until neutral. The product was then vacuum dried at 60 °C to obtain dopamine-coated silicon carbide whiskers, denoted 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 until homogeneous. 20–40 mL of a methanol solution containing 0.291–0.582 g of cobalt nitrate hexahydrate and 0.5–1 g of polyvinylpyrrolidone was added dropwise and stirred until homogeneous. 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 filtration, washed, and dried to obtain dopamine-coated silicon carbide whiskers with ZIF-67 crystals loaded on the surface, denoted as SiCw@PDA@ZIF-67.

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

[0011] Place 0.1–0.2 g of SiCw@PDA@ZIF-67 obtained in step 2 into a tube furnace, add 1–2 g of dicyandiamide, and perform high-temperature heat treatment 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 of PPTA fiber and 0.06–0.6 g of KOH were added to a mixture of 0.8–3.2 mL of H₂O and 40–80 mL of DMSO, and the mixture was magnetically stirred until homogeneous to obtain an ANF dispersion. The SiCw@C@CNT filler obtained in step 3 was added to the ANF dispersion and ultrasonically treated. The resulting mixture was dropped into water, and SiCw@C@CNT / ANF was precipitated by mechanical stirring. The product was separated by filtration. 50–100 mg of SiCw@C@CNT / ANF was added to 100–150 mL of H₂O and dispersed evenly using a homogenizer to obtain an aqueous suspension of SiCw@C@CNT / ANF. Finally, the aqueous suspension of SiCw@C@CNT / ANF was filtered through a polytetrafluoroethylene membrane to obtain a SiCw@C@CNT / ANF thermally conductive composite film.

[0014] Preferably, in step 3, the high-temperature heat treatment involves heating to 1200–1350°C and holding at that temperature for 2–6 hours.

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

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

[0017] The beneficial effects of this invention are reflected in:

[0018] This invention prepares SiCw@C@CNT hybrid fillers by in-situ growth of carbon nanotubes on the surface of silicon carbide whiskers coated with dopamine carbide. The dopamine carbide 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. Furthermore, by constructing a layered structure with ANF through vacuum filtration self-assembly, the thermal conductivity of the composite material is significantly improved. Attached Figure Description

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

[0020] Figure 2 This is a SEM image of the 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 This is a comparison chart of the thermal diffusivity of the samples obtained in Examples 1, 2, 3, and 4 and Comparative Examples 1, 2, 3, and 4 of the present invention. Detailed Implementation

[0025] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0026] Example 1

[0027] Step 1: Preparation of SiCw@PDA

[0028] 0.5 g of silicon carbide whiskers were added to 200 mL of distilled water and ultrasonically dispersed until homogeneous. 0.5 g of dopamine hydrochloride was dissolved in 50 mL of 0.01 M Tris-HCl solution, and then added to the silicon carbide whisker suspension. The pH was adjusted to 8.5 with 1 mol / L NaOH solution, and the mixture was stirred at 25 °C for 12 h. The product was separated by filtration and washed until neutral. It was then dried under vacuum at 60 °C to obtain dopamine-coated silicon carbide whiskers, denoted 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 methanol solution containing 0.437 g of cobalt nitrate hexahydrate and 0.5 g of polyvinylpyrrolidone was added dropwise and stirred evenly. Then, 20 mL of methanol solution containing 0.986 g of 2-methylimidazole was added dropwise and stirred for 3 h. The product was separated by filtration, washed and dried to obtain dopamine-coated silicon carbide whiskers with ZIF-67 crystals on the surface, denoted as SiCw@PDA@ZIF-67.

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

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

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

[0034] Add 0.2g PPTA fiber and 0.3g KOH to a mixture of 1.6mL H2O and 40mL DMSO, and stir magnetically until homogeneous (stirring speed 200rpm, stirring time 72 hours) to obtain a 5mg / mLANF dispersion. 5.6 mg of SiCw@C@CNT filler was added to 10 mL of LANF dispersion and sonicated until homogeneous. The resulting mixture was dropped into water, and SiCw@C@CNT / ANF was precipitated by mechanical stirring at 200 rpm. The product was separated by filtration. 50 mg of SiCw@C@CNT / ANF was added to 100 mL of H2O and dispersed evenly using a homogenizer to obtain an aqueous suspension of SiCw@C@CNT / ANF. Finally, the aqueous suspension of SiCw@C@CNT / ANF was filtered through a polytetrafluoroethylene membrane (pore size 0.22 μm, diameter 47 mm) to prepare a SiCw@C@CNT / ANF composite film, wherein the mass fraction of SiCw@C@CNT filler in the composite material was 10%.

[0035] Figure 1 This is a SEM image of the silicon carbide whiskers used in Example 1. Figure 2 The image shows the SEM image of the SiCw@PDA obtained in Example 1. It can be seen that the PDA particles are uniformly coated on the SiCw surface. Figure 3 The image shows 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-coated silicon carbide whiskers. Figure 4 The image shows the SEM image of SiCw@C@CNT obtained in Example 1. It can be seen that carbon nanotubes were successfully grown in situ on the surface of silicon carbide whiskers after high-temperature heat treatment. Figure 5 The image shows a 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. The silicon carbide whiskers with grown 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 embodiment, the SiCw@C@CNT / ANF composite material was prepared using the same method as in Example 1, except that in step 4, the amount of SiCw@C@CNT filler used was 12.5 mg, and the mass fraction of SiCw@C@CNT filler in the resulting composite material was 20 wt%.

[0038] Example 3

[0039] In this embodiment, the SiCw@C@CNT / ANF composite material was prepared using the same method as in Example 1, except that in step 4, the amount of SiCw@C@CNT filler used was 21.4 mg, and the mass fraction of SiCw@C@CNT filler in the resulting composite material was 30 wt%.

[0040] Example 4

[0041] In this embodiment, the SiCw@C@CNT / ANF composite material was prepared using the same method as in Example 1, except that in step 4, the amount of SiCw@C@CNT filler used was 33.3 mg, and the mass fraction of SiCw@C@CNT filler in the resulting composite material was 40 wt%.

[0042] Comparative Example 1

[0043] In this comparative example, SiCw / ANF composite materials were prepared according to the following steps:

[0044] 0.2 g PPTA fiber and 0.3 g KOH were added to a mixture of 1.6 mL H₂O and 40 mL DMSO and magnetically stirred until homogeneous (stirring speed 200 rpm, stirring time 72 hours) to obtain a 5 mg / mL LANF dispersion. 5.6 mg SiCw filler was added to 10 mL of the LANF dispersion and ultrasonically homogenized. The resulting mixture was dropped into water, and SiCw / ANF was precipitated by mechanical stirring at 200 rpm. The product was separated by filtration. 50 mg SiCw / ANF was added to 100 mL H₂O and dispersed uniformly using a homogenizer to obtain a SiCw / ANF aqueous suspension. Finally, the SiCw / ANF aqueous suspension was filtered through a polytetrafluoroethylene membrane (pore size 0.22 μm, diameter 47 mm) to prepare a SiCw / ANF composite film, wherein the mass fraction of SiCw filler in the composite material was 10%.

[0045] Comparative Example 2

[0046] This comparative example prepared SiCw / ANF composite material using the same method as Comparative Example 1, with the only difference being that the amount of SiCw filler used was 12.5 mg, and the mass fraction of SiCw filler in the resulting composite material was 20 wt%.

[0047] Comparative Example 3

[0048] This comparative example prepared SiCw / ANF composite material using the same method as Comparative Example 1, with the only difference being that the amount of SiCw filler used was 21.4 mg, and the mass fraction of SiCw filler in the resulting composite material was 30 wt%.

[0049] Comparative Example 4

[0050] The SiCw / ANF composite material was prepared in the same way 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 resulting composite material was 40 wt%.

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

[0052] Table 1. Thermal diffusivity of samples obtained from each embodiment and comparative example

[0053]

[0054] From Table 1 and Figure 6 It can be seen that, compared with Comparative Examples 1-4, the thermal diffusivity of the samples obtained in Examples 1-4 is significantly improved. The comparison shows that, compared with pure silicon carbide whiskers, silicon carbide whiskers with surface-loaded dopamine and carbon nanotubes exhibit a significantly improved thermal diffusivity at the same filler content. Furthermore, the thermal diffusivity of the composite material increases with increasing filler content. This is mainly because the in-situ growth of carbon nanotubes on the surface of silicon carbide whiskers effectively reduces the contact thermal resistance between fillers, thereby improving 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 within the protection scope of the present invention.

Claims

1. A method for preparing a SiCw@C@CNT / ANF thermally conductive composite material, characterized in that: Dopamine is first coated onto the surface of silicon carbide whiskers (SiCw). Then, ZIF-67 is uniformly loaded onto the dopamine-coated silicon carbide whisker surface through the adsorption of cations by catechol and amino groups in dopamine. High-temperature heat treatment then converts dopamine and ZIF-67 into graphene-like dopamine carbide and carbon nanotubes (CNTs), respectively, resulting in a silicon carbide whisker hybrid filler with surface-loaded dopamine and carbon nanotubes, denoted as SiCw@C@CNT. Finally, the filler is shear-mixed uniformly with aramid nanofibers (ANF) and then vacuum-filtered to obtain the SiCw@C@CNT / ANF thermally conductive composite material. The specific steps include the following: 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 until uniform. 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 the mixture was stirred at 25 °C for 12–24 h. The product was separated by filtration and washed until neutral. It was then vacuum dried at 60 °C to obtain dopamine-coated silicon carbide whiskers, 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 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 polyvinylpyrrolidone 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 hours. The product was separated by filtration, washed, and dried to obtain dopamine-coated silicon carbide whiskers with ZIF-67 crystals on the surface, denoted as SiCw@PDA@ZIF-67. Step 3: Preparation of SiCw@C@CNT Place 0.1~0.2 g of SiCw@PDA@ZIF-67 obtained in step 2 into a tube furnace, add 1~2 g of dicyandiamide, and perform high-temperature heat treatment 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 0.04–0.4 g of PPTA fiber and 0.06–0.6 g of KOH were added to a mixture of 0.8–3.2 mL of H₂O and 40–80 mL of DMSO, and the mixture was magnetically stirred until homogeneous to obtain an ANF dispersion. The SiCw@C@CNT filler obtained in step 3 was added to the ANF dispersion and ultrasonically treated. The resulting mixture was dropped into water, and SiCw@C@CNT / ANF was precipitated by mechanical stirring. The product was separated by filtration. 50–100 mg of SiCw@C@CNT / ANF was added to 100–150 mL of H₂O and dispersed evenly using a homogenizer to obtain an aqueous suspension of SiCw@C@CNT / ANF. Finally, the aqueous suspension of SiCw@C@CNT / ANF was filtered through a polytetrafluoroethylene membrane to obtain a SiCw@C@CNT / ANF thermally conductive composite film.

2. The preparation method according to claim 1, characterized in that: In step 3, the high-temperature heat treatment involves heating to 1200~1350℃ and holding at that temperature for 2~6 hours.

3. The preparation method according to claim 1, characterized in that: In step 4, the mass fraction of SiCw@C@CNT / ANF filler in the composite material is 10~40wt%.

4. The preparation method according to claim 1, characterized in that: In step 4, the polytetrafluoroethylene membrane has a pore size of 0.22 μm and a diameter of 47 mm.

5. A SiCw@C@CNT / ANF thermally conductive composite material obtained by the preparation method according to any one of claims 1 to 4.

Images