CN107141803A - The preparation method of carbon fiber carbon nano-tube array/silicones heat-conductive composite material - Google Patents

Abstract

The invention relates to a method for preparing a carbon fiber-carbon nanotube array/silicone resin heat-conducting composite material. The chopped carbon fiber with a length of 1 to 3 mm is immersed in a xylene solution of polydimethylsiloxane to prepare polydimethylsiloxane base siloxane/carbon fiber; the obtained polydimethylsiloxane/carbon fiber is placed in the constant temperature zone of the vacuum tube furnace, and after being pumped to a vacuum, argon is introduced as a protective gas, and the temperature is raised to obtain the silicon carbide/carbon fiber raw material; then The catalyst precursor solution prepared by dissolving ferrocene in xylene solution is pushed into the vacuum tube furnace and kept stable to obtain carbon fiber/carbon nanotube array composite powder; The nanotube array is combined with the silicone resin glue to obtain a carbon fiber-carbon nanotube array/silicone resin heat-conducting composite material. High thermal conductivity carbon composite material with thermal conductivity greater than 10W/(m·K) along the material thickness direction and greater than 3W/(m·K) along the horizontal direction.

Description

Preparation method of carbon fiber-carbon nanotube array/silicone resin heat-conducting composite material

technical field

The invention relates to a method for preparing a carbon fiber-carbon nanotube array/silicone resin heat-conducting composite material, in particular to a method for preparing a heat-conducting pad by vertically growing a carbon nanotube array on a carbon fiber and oriented and compounding it with a silicone resin.

Background technique

Efficient heat conduction and heat dissipation have become critical issues in the field of thermal management materials in the 21st century. For example, during the working process of the heat-generating device structure, due to the resistance, thermal resistance, electronic eddy current and other effects of the device itself or the influence of the external environment, a large amount of heat is generated and accumulated, especially in the part where the device element density is extremely high and the heat dissipation space is narrow. The heat flux density will be particularly large, resulting in an extremely unbalanced temperature distribution of the overall equipment, which puts forward higher and higher requirements for thermally conductive materials, and whether the heat generated by the device can be discharged in time, and whether the heat dissipation of the device is uniform and efficient greatly affects the quality of electronic equipment , performance and life. In order to dissipate the heat in time, we urgently need to develop new heat-conducting materials with lighter weight, higher thermal conductivity and better performance.

Carbon fiber is a fibrous one-dimensional nanomaterial obtained by preoxidation and high-temperature graphitization of pitch-based or acrylonitrile-based organic fibers. Due to the regular and orderly graphite atomic layer of carbon fiber, there are less obstacles to phonon conduction, fewer in-plane defects, and high thermal conductivity. Therefore, the use of carbon fiber to prepare carbon-based high thermal conductivity materials has become the focus of research, and similar Grant or publication of a patent. Invention patents such as CN105274698A, CN105972685A, and CN106304444A authorized by the State Intellectual Property Office of the People's Republic of China have announced the technology of using carbon fiber to prepare thermally conductive materials.

The invention patents mentioned above only disclose the traditional carbon fiber preparation method and composite process, and only obtain graphite heat-conducting materials with thermal anisotropy. For the graphite sheet of carbon fiber, the lattice vibration of carbon atoms is the basis for the heat conduction of the material, so the phonon transmission in the carbon fiber material can only be conducted at high speed along the graphite crystal plane, that is, the carbon fiber axis, while for the graphite crystal plane layer, Excessive distance seriously affects the conduction of phonons. After being processed by the fiber-forming process of organic raw materials, the graphene crystal plane is oriented along the fiber axis under the action of external force, so in carbon fibers, only along the fiber axis has high thermal conductivity (greater than 900W/(m·K)), The thermal conductivity along the radial direction of the fiber is very low, less than 15W/(m·K). Chinese patent applications CN105274698A, CN105972685A and other carbon fiber heat-conducting materials have thermal conductivity in the horizontal direction below 10W/(m·K). Therefore, the high anisotropy of the thermal conductivity of the material obtained in the existing published invention patents is far from meeting the requirements of large-scale computers and highly integrated electronic devices on the thermal conductivity of thermally conductive materials. Based on the existing advantages of carbon materials, a carbon material is developed. It is particularly important to have a material with high thermal conductivity and low anisotropy in both the horizontal direction and the thickness direction.

Contents of the invention

The present invention aims at the problem that the thermal conductivity of the polymer-based heat conduction sheet prepared by the existing carbon fiber or carbon nanotube is too low along the horizontal direction, and provides a material with high thermal conductivity along the horizontal direction and thickness direction of the material, that is, low thermal conductivity isotropic An anisotropic thermally conductive polymer-based carbon composite material (as shown in FIG. 1 ) and a preparation method thereof. Thermally conductive carbon composite materials with thermal conductivity of 10W/(m·K) and 3W/(m·K) along the material thickness direction and horizontal direction respectively.

The present invention adopts following technical scheme:

A method for preparing a carbon fiber-carbon nanotube array/silicone resin thermally conductive composite material, the steps are as follows:

1) Immerse chopped carbon fibers with a length of 1-3mm in the xylene solution of polydimethylsiloxane, stir at room temperature, filter with suction, put the filter cake in a blast drying oven and dry it at 50-70°C, Obtain polydimethylsiloxane/carbon fiber;

2) Place the polydimethylsiloxane/carbon fiber obtained in step 1) in the constant temperature zone of the vacuum tube furnace, pump it to a vacuum, and then pass in argon as a protective gas, and control the temperature rise by the program at 10-15°C/min Raise the temperature to 1100-1400°C at a uniform speed and hold it for 0.5-2 hours to obtain silicon carbide/carbon fiber raw materials; then cool down the tube furnace to 700-900°C, and push the catalyst precursor solution made of ferrocene dissolved in xylene solution into the In a vacuum tube furnace with stable heat preservation, the growth of carbon nanotube fiber bundles is carried out, and then the carbon fiber/carbon nanotube array composite powder is obtained after cooling down to room temperature;

3) Add the carbon nanotube array/carbon fiber composite powder to the electrostatic flocking equipment, and electrostatically orientate the carbon nanotube array/carbon fiber composite powder on the sticky substrate with a voltage of 2~10kV to make the arrangement density of the carbon nanotube array/carbon fiber composite powder reach 1~3g/m ^2. Composite the obtained carbon fiber-carbon nanotube array vertically oriented on the sticky substrate with silicone resin glue, and solidify at a temperature of 70-120° C. to obtain a carbon fiber-carbon nanotube array/silicone heat-conducting composite material.

The concentration of the xylene solution of polydimethylsiloxane in the step 1) is 0.1-0.3 g/ml.

In the step 1), the stirring rate is 300-600 r/min, and the stirring time is 10-30 minutes.

In the step 1), blow dry for 3 to 5 hours.

In the step 2), ferrocene is dissolved in xylene solution to make the concentration 0.02-0.05g/ml.

In the step 2), the catalyst precursor liquid is pushed into the vacuum tube furnace at a speed of 0.2-0.6 ml/min, and kept stably for 10-60 minutes.

The curing time in the step 3) is 0.5-2 hours.

The air pressure in the tube furnace is lower than 20Pa.

The carbon fiber-carbon nanotube array/silicone resin heat-conducting composite material prepared by the present invention is an oriented carbon nanotube array with a length greater than 20 μm and an array density greater than 2×10 ⁸ cm ^-2 ; the thermal conductivity is greater than 10W/(m· K), a thermally conductive carbon composite material greater than 3W/(m·K) in the horizontal direction.

The specific instructions are as follows:

(1) Growth of carbon nanotube arrays: adjust process parameters to prepare aligned carbon nanotube arrays with a length greater than 20 μm and an array density greater than 2×10 ⁸ cm ^-2 ; since carbon fibers have high thermal conductivity along the axial direction, the radial thermal conductivity Very low, after the carbon nanotube array is grown on the surface of the carbon fiber, the carbon nanotube array will be perpendicular to the carbon fiber, and the high thermal conductivity of the carbon nanotube array along the radial direction of the carbon fiber can be used to realize the level of carbon fiber-carbon nanotube array/silicone thermal conductivity composite material Directional heat flow transfer, which is very beneficial to improve the thermal conductivity of the composite material along the horizontal direction and reduce its thermal anisotropy;

Through the electrostatic orientation of the carbon fiber-carbon nanotube array/silicone thermal conductive composite material in the above steps, the dual orientation of the carbon fiber with high thermal conductivity in the axial direction and the carbon nanotube array with high thermal conductivity in the radial direction of the carbon fiber is realized, and the obtained High thermal conductivity carbon composite material with thermal conductivity greater than 10W/(m·K) along the material thickness direction and greater than 3W/(m·K) along the horizontal direction.

Beneficial effects of the present invention: the matrix raw material carbon fiber of the present invention is easy to obtain, and the growth of the carbon nanotube array is simple and controllable. In the present invention, the ordering, layering, graphitization and material molding of the microstructure can be efficiently completed, and the carbon-carbon composite material with low thermal conductivity anisotropy can be obtained, and its thermal conductivity is far superior to that of traditional polymers. based thermally conductive carbon composites.

Description of drawings

Fig. 1 is the microcosmic schematic view of the high thermal conductivity polymer-based carbon composite material of the present invention, including composite form and heat conduction direction;

Fig. 2 is a scanning electron microscope picture of a carbon fiber sample with carbon nanotube arrays grown on the surface.

detailed description

Provide 5 embodiments of the present invention below, be further description of the present invention, rather than limit the scope of the present invention.

1) Immerse commercially available chopped carbon fibers with a length of 1-3 mm in a xylene solution with a polydimethylsiloxane concentration of 0.1-0.3 g/ml, stir at 300-600 r/min at room temperature for 10-30 minutes, After suction filtration, the filter cake is placed in a blast drying oven and dried at 50-70°C for 3-5 hours to prepare polydimethylsiloxane/carbon fiber;

2) Place the polydimethylsiloxane/carbon fiber obtained in step 1) in the constant temperature zone of the vacuum tube furnace, pump it to a vacuum, and then pass in argon as a protective gas, and control the temperature rise by the program at 10-15°C/min Raise the temperature to 1100-1400°C at a uniform speed and keep it warm for 0.5-2 hours to obtain silicon carbide/carbon fiber raw materials; after the tube furnace cools down to 700-900°C, dissolve ferrocene in xylene solution to make the concentration 0.02-0.05g /ml of catalyst precursor solution is pushed into the vacuum tube furnace at a constant speed of 0.2-0.6ml/min and kept stable for 10-60 minutes to grow carbon nanotube fiber bundles. After cooling down to room temperature, carbon fiber/carbon nanotube array composites are obtained. Powder, as shown in Figure 2: the carbon nanotube array is arranged vertically and radially with the carbon fiber as the axis;

3) Add the carbon nanotube array/carbon fiber composite powder into the electrostatic flocking equipment, and electrostatically orientate with a voltage of 2-10kV for 0.5-2 minutes, so that the arrangement density of the carbon nanotube array/carbon fiber composite powder on the sticky substrate reaches 1 ～3g/m ² ; the obtained carbon fiber-carbon nanotube array uniformly oriented vertically on the adhesive substrate is compounded with silicone resin glue, cured at a temperature of 70-120°C for 0.5-2 hours, and finally carbon fiber-carbon nanotubes are obtained Tube Array/Silicone Thermally Conductive Composite.

The finally prepared carbon fiber-carbon nanotube array/silicone resin heat-conducting composite material is a flexible composite heat-conducting gasket composed of carbon nanotube array/carbon fiber orientation arrangement. In the composite material, vertically oriented carbon fibers provide a thermal conduction path of the composite material along the thickness direction, and horizontally oriented carbon nanotube arrays provide the thermal conduction performance of the composite material in the horizontal direction.

Example 1

Immerse commercially available chopped carbon fibers with a length of 1 mm into a xylene solution with a polydimethylsiloxane concentration of 0.1 g/ml, stir at 300 r/min at room temperature for 10 minutes, and filter the filter cake into a blower Dry in a drying oven at 50°C for 3 hours to prepare polydimethylsiloxane/carbon fiber; place the polydimethylsiloxane/carbon fiber prepared in the first step in the constant temperature zone of the vacuum tube furnace and pump it to vacuum Afterwards, argon gas was introduced as a protective gas, and the temperature was raised by program control, and the temperature was raised to 1100°C at a constant speed of 10°C/min and kept for 0.5 hours to obtain silicon carbide/carbon fiber raw materials, and then the tube furnace was cooled to 700°C, and the two Dissolve ferrocene in xylene solution to make a catalyst precursor solution with a concentration of 0.02g/ml, push it into a vacuum tube furnace at a constant speed of 0.2ml/min and keep it stable for 10 minutes to grow carbon nanotube fiber bundles, and wait to cool down to room temperature Finally, the carbon fiber/carbon nanotube array composite powder is obtained; the carbon nanotube array/carbon fiber composite powder is added to the electrostatic flocking device, and the voltage of 2kV is electrostatically oriented for 0.5 minutes, so that the carbon nanotube array/carbon fiber composite powder is on the sticky substrate The arrangement density reaches 1g/m ² , and the obtained carbon fiber-carbon nanotube array uniformly oriented vertically on the adhesive substrate is compounded with silicone resin glue, cured at 70°C for 0.5 hours, and finally the carbon fiber-carbon nanotube array is obtained Array/silicon resin heat-conducting composite material, the test thermal conductivity is 10W/(m·K) along the axial direction of the material, and 3W/(m·K) along the radial direction.

Example 2

Immerse commercially available chopped carbon fibers with a length of 3 mm into a xylene solution with a polydimethylsiloxane concentration of 0.3 g/ml, stir at 600 r/min at room temperature for 30 minutes, and filter the filter cake into a blower Dry in a drying oven at 70°C for 5 hours to prepare polydimethylsiloxane/carbon fiber; place the polydimethylsiloxane/carbon fiber prepared in the first step in the constant temperature zone of the vacuum tube furnace and pump it to vacuum Afterwards, argon gas was introduced as a protective gas, and the temperature was raised by program control, and the temperature was raised to 1400°C at a constant speed of 15°C/min and kept for 2 hours to obtain silicon carbide/carbon fiber raw materials, and then the tube furnace was cooled to 900°C, and the two Dissolve ferrocene in xylene solution to make a catalyst precursor solution with a concentration of 0.05g/ml, push it into a vacuum tube furnace at a constant speed of 0.6ml/min and keep it stable for 60 minutes to grow carbon nanotube fiber bundles, and wait to cool down to room temperature Finally, the carbon fiber/carbon nanotube array composite powder is obtained; the carbon nanotube array/carbon fiber composite powder is added to the electrostatic flocking device, and the voltage of 10kV is electrostatically oriented for 2 minutes, so that the carbon nanotube array/carbon fiber composite powder is on the sticky substrate The arrangement density reaches 3g/m ² , and the obtained carbon fiber-carbon nanotube array uniformly oriented vertically on the adhesive substrate is compounded with silicone resin glue, and cured at a temperature of 120°C for 2 hours to finally obtain carbon fiber-carbon nanotube Array/silicon resin thermally conductive composite material, the thermal conductivity of the test is 21W/(m·K) along the axial direction of the material, and 7.8W/(m·K) along the radial direction.

Example 3

Immerse commercially available chopped carbon fibers with a length of 2 mm into a xylene solution with a polydimethylsiloxane concentration of 0.2 g/ml, stir at 500 r/min at room temperature for 20 minutes, and filter the filter cake into a blower Dry in a drying oven at 60°C for 4 hours to prepare polydimethylsiloxane/carbon fiber; place the polydimethylsiloxane/carbon fiber prepared in the first step in the constant temperature zone of the vacuum tube furnace and pump it to vacuum Afterwards, argon gas was introduced as a protective gas, and the temperature was raised by program control, and the temperature was raised to 1350°C at a constant speed of 13°C/min and kept for 1 hour to obtain silicon carbide/carbon fiber raw materials, and then the tube furnace was cooled to 800°C. Dissolve iron in xylene solution to make a catalyst precursor solution with a concentration of 0.03g/ml and push it into a vacuum tube furnace at a constant speed of 0.4ml/min and keep it stable for 40 minutes to grow carbon nanotube fiber bundles. After cooling down to room temperature The carbon fiber/carbon nanotube array composite powder is obtained; the carbon nanotube array/carbon fiber composite powder is added to the electrostatic flocking device, and the voltage of 7kV is electrostatically oriented for 1.5 minutes, so that the carbon nanotube array/carbon fiber composite powder on the sticky substrate The arrangement density reaches 1.5g/m ² , and the obtained carbon fiber-carbon nanotube array uniformly oriented vertically on the adhesive substrate is compounded with silicone resin glue, cured at 100°C for 1.5 hours, and finally carbon fiber-carbon nanotubes are obtained Array/silicon resin heat-conducting composite material, the test thermal conductivity is 13W/(m·K) along the axial direction of the material, and 4.2W/(m·K) along the radial direction.

Example 4

Immerse commercially available chopped carbon fibers with a length of 1mm into a xylene solution with a polydimethylsiloxane concentration of 0.3g/ml, stir at 500r/min at room temperature for 16 minutes, and filter the filter cake into a blower Dry in a drying oven at 60°C for 3 hours to prepare polydimethylsiloxane/carbon fiber; place the polydimethylsiloxane/carbon fiber prepared in the first step in the constant temperature zone of the vacuum tube furnace and pump it to vacuum Afterwards, argon gas was introduced as a protective gas, and the temperature was raised by program control, and the temperature was raised to 1100°C at a constant speed of 11°C/min and kept for 2 hours to obtain silicon carbide/carbon fiber raw materials, and then the tube furnace was cooled to 850°C, and the two Dissolve ferrocene in xylene solution to make a catalyst precursor solution with a concentration of 0.04g/ml, push it into a vacuum tube furnace at a constant speed of 0.3ml/min and keep it stable for 26 minutes to grow carbon nanotube fiber bundles, and wait to cool down to room temperature Finally, the carbon fiber/carbon nanotube array composite powder is obtained; the carbon nanotube array/carbon fiber composite powder is added to the electrostatic flocking device, and the voltage of 9kV is electrostatically oriented for 2 minutes, so that the carbon nanotube array/carbon fiber composite powder is on the sticky substrate. The arrangement density reaches 1.7g/m ² , and the obtained carbon fiber-carbon nanotube array uniformly oriented vertically on the adhesive substrate is compounded with silicone resin glue, cured at 120°C for 1 hour, and finally the carbon fiber-carbon nanotube array is obtained. Tube array/silicon resin heat-conducting composite material, the test thermal conductivity is 17.3W/(m·K) along the axial direction of the material, and 4W/(m·K) along the radial direction.

Example 5

Immerse commercially available chopped carbon fibers with a length of 3 mm into a xylene solution with a polydimethylsiloxane concentration of 0.2 g/ml, stir at 500 r/min at room temperature for 15 minutes, and filter the filter cake into a blower Dry in a drying oven at 70°C for 3 hours to prepare polydimethylsiloxane/carbon fiber; place the polydimethylsiloxane/carbon fiber prepared in the first step in the constant temperature zone of the vacuum tube furnace and pump it to vacuum Afterwards, argon gas was introduced as a protective gas, and the temperature was raised by program control, and the temperature was raised to 1300°C at a constant speed of 14°C/min and kept for 1.5 hours to obtain the silicon carbide/carbon fiber raw material, and then the tube furnace was cooled to 900°C. Dissolve iron in xylene solution to make a catalyst precursor solution with a concentration of 0.02g/ml and push it into a vacuum tube furnace at a constant speed of 0.6ml/min and keep it stable for 60 minutes to grow carbon nanotube fiber bundles. After cooling down to room temperature The carbon fiber/carbon nanotube array composite powder is obtained; the carbon nanotube array/carbon fiber composite powder is added to the electrostatic flocking device, and the voltage of 10kV is electrostatically oriented for 0.9 minutes, so that the carbon nanotube array/carbon fiber composite powder on the sticky substrate The arrangement density reaches 1g/m ² , and the obtained carbon fiber-carbon nanotube array uniformly oriented vertically on the adhesive substrate is compounded with silicone resin glue, cured at 110°C for 2 hours, and finally the carbon fiber-carbon nanotube array is obtained /Silicone resin heat-conducting composite material, the thermal conductivity of the test is 18.6W/(m·K) along the axial direction of the material, and 7.5W/(m·K) along the radial direction.

The preparation method of the carbon fiber-carbon nanotube array/silicone resin heat-conducting composite material disclosed and proposed by the present invention can be realized by those skilled in the art by referring to the content of this article and appropriately changing the conditions and routes, although the method and preparation technology of the present invention have passed The preferred implementation examples are described, and it is obvious that those skilled in the art can modify or recombine the methods and technical routes described herein without departing from the content, spirit and scope of the present invention to realize the final preparation technology. In particular, it should be pointed out that all similar substitutions and modifications will be obvious to those skilled in the art, and they are all considered to be included in the spirit, scope and content of the present invention.

Claims (9)

1. a preparation method of carbon fiber-carbon nanotube array/silicone resin thermally conductive composite material, characterized in that the steps are as follows: 1) Immerse chopped carbon fibers with a length of 1-3mm in the xylene solution of polydimethylsiloxane, stir at room temperature, filter with suction, put the filter cake in a blast drying oven and dry it at 50-70°C, Obtain polydimethylsiloxane/carbon fiber; 2) Place the polydimethylsiloxane/carbon fiber obtained in step 1) in the constant temperature zone of the vacuum tube furnace, pump it to a vacuum, and then pass in argon as a protective gas, and control the temperature rise by the program at 10-15°C/min Raise the temperature to 1100-1400°C at a uniform speed and hold it for 0.5-2 hours to obtain silicon carbide/carbon fiber raw materials; then cool down the tube furnace to 700-900°C, and push the catalyst precursor solution made of ferrocene dissolved in xylene solution into the vacuum tube In a type furnace with stable heat preservation, the growth of carbon nanotube fiber bundles is carried out, and then the carbon fiber/carbon nanotube array composite powder is obtained after cooling down to room temperature; 3) Add the carbon nanotube array/carbon fiber composite powder to the electrostatic flocking equipment, and electrostatically orientate the carbon nanotube array/carbon fiber composite powder on the sticky substrate with a voltage of 2~10kV to make the arrangement density of the carbon nanotube array/carbon fiber composite powder reach 1~3g/m ^2. Composite the obtained carbon fiber-carbon nanotube array vertically oriented on the sticky substrate with silicone resin glue, and solidify at a temperature of 70-120° C. to obtain a carbon fiber-carbon nanotube array/silicone heat-conducting composite material. 2. The method according to claim 1, characterized in that the concentration of the xylene solution of polydimethylsiloxane in step 1) is 0.1-0.3 g/ml. 3. The method according to claim 1, characterized in that in step 1), the stirring rate is 300-600 r/min, and the stirring time is 10-30 minutes. 4. The method according to claim 1, characterized in that in the step 1), the blast drying is performed for 3 to 5 hours. 5. The method according to claim 1, characterized in that in step 2), ferrocene is dissolved in xylene solution to make the concentration 0.02～0.05g/ml. 6. The method according to claim 1, characterized in that in step 2), the catalyst precursor liquid is pushed into the vacuum tube furnace at a speed of 0.2 to 0.6 ml/min, and is kept stable for 10 to 60 minutes. 7. The method according to claim 1, characterized in that the curing time in step 3) is 0.5 to 2 hours. 8. The method according to claim 1, characterized in that the air pressure in the tube furnace is lower than 20Pa. 9. The method according to claim 1, characterized in that the length of the prepared carbon fiber-carbon nanotube array/silicone resin heat-conducting composite material is greater than 20 μm, and the array density is greater than 2×10 ⁸ cm ^-2 oriented carbon nanotube array; thermal Thermally conductive carbon composite materials whose conductivity is greater than 10W/(m·K) along the thickness direction of the material and greater than 3W/(m·K) along the horizontal direction.