A method for improving the thermal conductivity of pitch-based carbon fiber composite materials in the thickness direction

Abstract

The present application belongs to the field of carbon fiber composite materials, and provides a method for improving the thickness direction thermal conductivity of asphalt-based carbon fiber composite materials. The purpose of the present application is to solve the problem of low thickness direction thermal conductivity of asphalt-based carbon fiber composite materials, and to improve their performance and reliability in the field of aerospace. The technical solution of the present application is: using chemical vapor deposition (CVD) method to prepare carbon nanotubes (CNT) with large aspect ratio on the surface of asphalt-based carbon fiber, thereby forming a new type of composite material with high thermal conductivity, low density and high temperature resistance. The innovation of the present application is: growing large aspect ratio CNT on the surface of asphalt-based carbon fiber, and constructing a heat conduction channel in the thickness direction of asphalt-based carbon fiber composite material, which significantly improves its thermal conductivity. The advantage of the present application is: simple and controllable method, excellent, stable and durable product performance, wide application and broad prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of carbon fiber composites, and particularly relates to a method for improving the thickness direction thermal conductivity of pitch-based carbon fiber composites. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of increasing an understanding of the general context of the present application and is not necessarily recognized in any form as an admission that this information constitutes prior art.

[0003] Ordinary carbon fiber composites have poor thickness direction heat conduction ability due to the low thermal conductivity of the fibers themselves and the discontinuity between the fibers, which seriously limits their application in the field of aerospace. At present, some studies are dedicated to modifying the surface of ordinary carbon fibers with carbon nanotubes, for example: patent CN116536597A discloses a method for in-situ generating carbon nanotubes on a short carbon fiber porous body with pyrolytic carbon by a chemical vapor deposition process, but due to the low thermal conductivity of ordinary carbon fibers and the shortness of carbon nanotubes, it is difficult to realize the application of carbon fiber composites in the field of heat conduction.

[0004] On the other hand, due to the strong inertness of the surface of pitch-based carbon fibers, it is difficult to load a sufficient amount of catalyst on the surface of pitch-based carbon fibers using traditional loading methods, which further affects the effect of growing carbon nanotubes by chemical vapor deposition. SUMMARY

[0005] In order to solve the above problems, the present application provides a method for improving the thickness direction thermal conductivity of pitch-based carbon fiber composites. The present application uses the chemical vapor deposition (CVD) method to prepare carbon nanotubes (CNT) with a large aspect ratio on the surface of pitch-based carbon fibers (PCF), and constructs a heat conduction channel in the thickness direction of the pitch-based carbon fiber composite, thereby significantly improving its thermal conductivity.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0007] The first aspect of the present application provides a method for improving the thickness direction thermal conductivity of pitch-based carbon fiber composites, comprising:

[0008] Dissolve NiCl2·6H2O in a methanol solution and stir uniformly to obtain a precursor solution;

[0009] The pitch-based carbon fibers are subjected to acid treatment, and then the carbon fibers are vertically immersed in the precursor solution for 24-32 hours, washed and dried to obtain NiCl2·6H2O@PCF;

[0010] The large aspect ratio carbon nanotubes are grown by CVD method with NiCl2.6H2O@PCF and melamine as carbon source and nitrogen source respectively, and CNT@PCF is obtained.

[0011] The CNT@PCF is fully infiltrated by resin, and is cured and formed, and the pitch-based carbon fiber composite material is obtained.

[0012] The large aspect ratio of the carbon nanotubes is greater than 250:1.

[0013] Because the pitch-based carbon fiber has strong surface inertness, the nickel-based catalyst is generally loaded by electroplating or surfactant at present, and the method is complex and the catalytic effect is poor. Therefore, the application researches and finds that: by dividing the acidified carbon fiber tows into many small tows and immersing in the methanol solution of NiCl2.6H2O in a vertical manner, the catalyst precursor NiCl2.6H2O can be uniformly loaded on the surface of PCF, and the uniformity of the growth of carbon nanotubes on the surface of PCF is improved.

[0014] In some embodiments, the concentration of NiCl2.6H2O in the precursor solution is 0.32M.

[0015] In some embodiments, the washing is performed by multiple times of washing with methanol.

[0016] In some embodiments, the drying condition is 80-90℃ for 16-24h.

[0017] In some embodiments, the mass ratio of melamine to NiCl2.6H2O@PCF is 16-24:1.

[0018] In some embodiments, the processing temperature of the CVD method is 450-750℃, and the holding time is 2-3h.

[0019] In some embodiments, the processing atmosphere of the CVD method is H2 / Ar mixed gas, and the proportion of H2 is 5%.

[0020] In some embodiments, the resin is mixed by epoxy resin and curing agent at a mass ratio of 131-150:40.

[0021] The second aspect of the application provides the pitch-based carbon fiber composite material prepared by the above method.

[0022] The third aspect of the application provides the application of the above pitch-based carbon fiber composite material in the field of aerospace.

[0023] Advantages of the application

[0024] (1) The present application utilizes chemical vapor deposition (CVD) method to prepare carbon nanotubes (CNT) with large aspect ratio on the surface of pitch-based carbon fiber (PCF), and constructs a heat conduction channel in the thickness direction of pitch-based carbon fiber composite material, thereby significantly improving the thermal conductivity.

[0025] (2) The preparation process of the present application is simple and controllable, and is suitable for the field of aerospace, and can be used for aircraft hot end, heat dissipation and other components, thereby improving the operation efficiency and safety of equipment.

[0026] (3) The present application uses CVD method to grow carbon nanotubes with large aspect ratio on the surface of pitch-based carbon fiber at a lower temperature; the carbon nanotubes with large aspect ratio play a connecting role between continuous fibers, and provide an effective path for heat transfer. BRIEF DESCRIPTION OF DRAWINGS

[0027] The drawings constituting a part of the specification of the present application are used to provide further understanding of the present application, and the exemplary embodiments of the present application and the description thereof are used to explain the present application, and do not constitute an improper limitation on the present application.

[0028] Figure 1 is a preparation flow chart of NiCl2·6H2O@PCF and CNT@PCF.

[0029] Figure 2 is a preparation flow chart of CNT@PCF / EP composite material. DETAILED DESCRIPTION

[0030] It should be pointed out that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0031] The present application will be further described in detail below in combination with specific examples, and it should be pointed out that the specific examples are used to explain the present application rather than limit the present application.

[0032] In the following examples, the H2 content in the H2 / Ar mixed gas is 5%, the curing agent is E200, the hydrogen equivalent is 44.3Lonza company, and the concentration of the catalyst precursor mixed solution is 0.32M.

[0033] Example 1

[0034] 1. Preparation of NiCl2·6H2O@PCF and CNT@PCF

[0035] NiCl2·6H2O was dissolved in methanol solution to obtain a 0.32 M catalyst precursor mixture, and stirred for 4 h with a magnetic stirrer to obtain a homogeneous solution. The acid-treated PCF was vertically immersed in the solution for 24 h to allow the catalyst precursor NiCl2·6H2O to be uniformly loaded on the surface of the PCF. Finally, the PCF was taken out of the solution, repeatedly washed with methanol, and then dried in an oven at 80 °C for 24 h to obtain NiCl2·6H2O@PCF. The NiCl2·6H2O@PCF was placed on one side of a porcelain boat, and melamine (mass ratio of melamine to NiCl2·6H2O@PCF was 20:1) was placed on the other side as a carbon and nitrogen source for the growth of CNTs. The porcelain boat was placed in the center of a tube carbonization furnace Figure 1 ), and the furnace was evacuated to vacuum before heating, and then H2 / Ar mixed gas (H2 accounted for 5%) was introduced from the melamine side. The temperature was raised to 450 °C at a rate of 5 °C / min, and held for 2 h. The prepared sample was named CNT@PCF -450 .

[0036] 2. Preparation of CNT@PCF / EP composite material

[0037] The epoxy resin and curing agent (E200 hydrogen equivalent: 44.3 g / L, Lonza Company) were mixed according to a mass ratio of 131:40 to obtain a resin matrix system. As shown in Figure 2 , the prepared CNT@PCF was fully infiltrated with the pre-configured resin (the fiber amount was calculated as 60% by volume). Subsequently, it was placed in a mold for curing, and the curing process was 90 °C / 1 h + 120 °C / 2 h + 150 °C / 3 h. After natural cooling, the sample was taken out, and the sample was named CNT@PCF -450 / EP.

[0038] Example 2

[0039] 1. Preparation of NiCl2·6H2O@PCF and CNT@PCF

[0040] NiCl2·6H2O was dissolved in methanol solution to obtain a catalyst precursor mixture, and stirred for 4 h with a magnetic stirrer to obtain a homogeneous solution. The acid-treated PCF was vertically immersed in the solution for 24 h to allow the catalyst precursor NiCl2·6H2O to be uniformly loaded on the surface of the PCF. Finally, the PCF was taken out of the solution, repeatedly washed with methanol, and then dried in an oven at 80°C for 24 h to obtain NiCl2·6H2O@PCF. The NiCl2·6H2O@PCF was placed on one side of a porcelain boat, and melamine (mass ratio of melamine to NiCl2·6H2O@PCF was 20:1) was placed on the other side as a carbon source and nitrogen source for the growth of CNT. The porcelain boat was placed in the center of a tube-type carbonization furnace, and the gas pressure in the furnace was first pumped to vacuum before heating, and then H2 / Ar mixed gas was introduced from the melamine side. The temperature was raised to 550°C at a rate of 5°C / min, and held for 2 h. The prepared sample was named CNT@PCF -550 .

[0041] 2. Preparation of CNT@PCF / EP composite material

[0042] The epoxy resin and curing agent were mixed in a mass ratio of 131:40 to obtain a resin matrix system. The prepared CNT@PCF was fully infiltrated with the pre-configured resin (the amount of fiber was calculated as 60% by volume). Then it was placed in a mold for curing, and the curing process was 90°C / 1h + 120°C / 2h + 150°C / 3h. After natural cooling, the sample was taken out, and the sample was named CNT@PCF -550 / EP.

[0043] Example 3

[0044] 1. Preparation of NiCl2·6H2O@PCF and CNT@PCF

[0045] NiCl2·6H2O was dissolved in methanol solution to obtain a catalyst precursor mixture, and stirred for 4 h with a magnetic stirrer to obtain a homogeneous solution. The acid-treated PCF was vertically immersed in the solution for 24 h to allow the catalyst precursor NiCl2·6H2O to be uniformly loaded on the surface of the PCF. Finally, the PCF was taken out of the solution, repeatedly washed with methanol, and then dried in an oven at 80°C for 24 h to obtain NiCl2·6H2O@PCF. The NiCl2·6H2O@PCF was placed on one side of a porcelain boat, and melamine (mass ratio of melamine to NiCl2·6H2O@PCF was 20:1) was placed on the other side as a carbon source and nitrogen source for the growth of CNT. The porcelain boat was placed in the center of a tube-type carbonization furnace, and the gas pressure in the furnace was first pumped to vacuum before heating, and then H2 / Ar mixed gas was introduced from the melamine side. The temperature was raised to 650°C at a rate of 5°C / min, and held for 2 h. The prepared sample was named CNT@PCF -650 .

[0046] 2. Preparation of CNT@PCF / EP composite material

[0047] The epoxy resin and curing agent were mixed in a mass ratio of 131:40 to obtain a resin matrix system. The prepared CNT@PCF was fully infiltrated with the pre-configured resin (the fiber amount was calculated as 60% by volume). Subsequently, it was placed in a mold for curing, and the curing process was 90℃ / 1h+120℃ / 2h+150℃ / 3h. After natural cooling, the sample was taken out, and the sample was named CNT@PCF / EP. -650

[0048] Example 4

[0049] 1. Preparation of NiCl2·6H2O@PCF and CNT@PCF

[0050] NiCl2·6H2O was dissolved in a methanol solution to obtain a catalyst precursor mixed solution, and a magnetic stirrer was used for stirring for 4h to obtain a homogeneous solution. The acid-treated PCF was vertically soaked in the solution for 24h to make the catalyst precursor NiCl2·6H2O uniformly loaded on the surface of the PCF. Finally, the PCF was taken out of the solution, repeatedly washed with methanol, and then dried in an oven at 80℃ for 24h to obtain NiCl2·6H2O@PCF. The NiCl2·6H2O@PCF was placed on one side of a porcelain boat, and melamine (the mass ratio of melamine to NiCl2·6H2O@PCF was 20:1) was placed on the other side as a carbon source and nitrogen source for the growth of CNT. The porcelain boat was placed in the center of a tube-type carbonization furnace, and the gas pressure in the furnace was first pumped to vacuum before heating, and then H2 / Ar mixed gas was introduced from the melamine side. The temperature was raised to 750℃ at a rate of 5℃ / min, and the temperature was maintained for 2h. The prepared sample was named CNT@PCF -750 .

[0051] 2. Preparation of CNT@PCF / EP composite material

[0052] The epoxy resin and curing agent were mixed in a mass ratio of 131:40 to obtain a resin matrix system. The prepared CNT@PCF was fully infiltrated with the pre-configured resin (the fiber amount was calculated as 60% by volume). Subsequently, it was placed in a mold for curing, and the curing process was 90℃ / 1h+120℃ / 2h+150℃ / 3h. After natural cooling, the sample was taken out, and the sample was named CNT@PCF / EP. -750

[0053] Experimental example

[0054] The thermal conductivity was tested according to the provisions in GB / T22588-2008, and the performance of the composite material is shown in Table 1.

[0055] Table 1​​

[0056] Numbering Thermal conductivity W / (m . K) Example 1 2.16 Example 2 2.88 Example 3 3.07 Example 4 2.20

[0057] The experimental results show that under the condition of CVD temperature of 650 DEG C, the carbon nanotubes with large length-diameter ratio (250:1) grown on the surface of pitch-based carbon fiber are uniform and long, and play a connecting role between the fibers, so that the heat is effectively transmitted in the thickness direction of the composite material.

[0058] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and various modifications and changes can be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of improving the in-thickness thermal conductivity of pitch-based carbon fiber composites, characterized by, The method comprises the following steps: dissolving NiCl2·6H2O in a methanol solution, stirring uniformly to obtain a precursor solution; acid-treating pitch-based carbon fibers, then vertically immersing the carbon fibers in the precursor solution for 24-32 hours, washing and drying to obtain NiCl2·6H2O@PCF; growing carbon nanotubes with a large aspect ratio by using melamine as a carbon source and a nitrogen source through a CVD method to obtain CNT@PCF; the treatment temperature of the CVD method is 650-750 DEG C; fully immersing the CNT@PCF in a resin, and curing and forming, thus obtaining the product; wherein the aspect ratio of the carbon nanotubes with a large aspect ratio is greater than 200:

1.

2. The method of claim 1, wherein the pitch-based carbon fiber composite material is a carbon fiber reinforced polymer. In the precursor solution, the concentration of NiCl2·6H2O is 0.32 M.

3. The method of claim 1, wherein the pitch-based carbon fiber composite material is a carbon fiber reinforced polymer. The washing is performed by using methanol for multiple times.

4. The method of claim 1, wherein the pitch-based carbon fiber composite material is a carbon fiber reinforced polymer. The drying condition is 80-90 DEG C for 16-24 hours.

5. The method of claim 1, wherein the pitch-based carbon fiber composite material is a carbon fiber reinforced polymer. The mass ratio of melamine to NiCl2·6H2O@PCF is 16-24:

1.

6. The method of claim 1, wherein the pitch-based carbon fiber composite material is a carbon fiber reinforced polymer. The holding time of the CVD method is 2-3 hours.

7. The method of claim 1, wherein the pitch-based carbon fiber composite material is a carbon fiber reinforced polymer. The atmosphere of the CVD method is H2 / Ar mixed gas, and the proportion of H2 is 5%.

8. The method of claim 1, wherein the pitch-based carbon fiber composite material is a carbon fiber reinforced polymer. The resin is obtained by mixing epoxy resin and a curing agent at a mass ratio of 131-150:

40.

9. The pitch-based carbon fiber composite material prepared by the method in any one of claims 1-8.

10. The pitch-based carbon fiber composite material in claim 9 is applied in the field of aerospace.

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