CN112235999B - Preparation method of carbon nano tube heat conducting fin - Google Patents
Preparation method of carbon nano tube heat conducting fin Download PDFInfo
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- CN112235999B CN112235999B CN202010953257.4A CN202010953257A CN112235999B CN 112235999 B CN112235999 B CN 112235999B CN 202010953257 A CN202010953257 A CN 202010953257A CN 112235999 B CN112235999 B CN 112235999B
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Abstract
The invention relates to a preparation method of a carbon nano tube heat conducting fin, which comprises the following steps: forming an orientation-oriented carbon nanotube array on a substrate, wherein a plurality of micropores which are arranged at specified intervals and used for filling raw materials of thermosetting polymer materials are arranged on the substrate, and carbon nanotubes in the carbon nanotube array; injecting glue on the glue injection surface to enable the thermosetting high polymer material to flow towards the direction close to the free ends of the carbon nano tubes through the micropores and fill gaps among the carbon nano tubes; stopping pouring the glue and turning over the substrate when the distance between the thermosetting high polymer material flowing along the carbon nano tube and the free end is 0.02-0.2 mm; and curing the thermosetting polymer material positioned among the carbon nano tubes and separating the cured carbon nano tube array from the substrate to obtain the carbon nano tube heat-conducting fin. The preparation method is simple and convenient, and the prepared carbon nano tube heat conducting sheet has high heat conducting property.
Description
Technical Field
The invention relates to the technical field of carbon nanotubes, in particular to a preparation method of a carbon nanotube heat conducting fin.
Background
With the continuous reduction of the feature size and the great improvement of the performance of microelectronic devices, the performance of the devices is easily reduced or even fails due to the large amount of heat accumulated in a microelectronic system in a short time, and the development of microelectronic technology is restricted.
The carbon nano tube has the advantages of high thermal conductivity, high temperature resistance, flexibility and the like, and is expected to become a material choice for solving the heat dissipation problem. Early carbon nanotube heat conductive sheets were made by mixing carbon nanotubes into a polymer material such as resin or rubber to form a sheet. However, due to the low thermal conductivity of these high molecular materials and the anisotropic thermal conductivity of carbon nanotubes, it is difficult to achieve a sufficiently high thermal conductivity of the carbon nanotube hybrid material.
With the progress of science and technology, it is found that the carbon nanotube array grown in an oriented orientation mode has good radial thermal conductivity, wherein the thermal conductivity of a single carbon nanotube can reach 6000W/(m.K) theoretically, so that the carbon nanotubes on the carbon nanotube heat conducting sheet are gradually presented in the form of the carbon nanotube array arranged in an oriented orientation mode. However, in practical applications, it is found that the thermal conductivity of the carbon nanotube thermal conductive sheet in the form of the carbon nanotube array with the carbon nanotubes aligned in the orientation direction is not ideal and is still low.
Disclosure of Invention
Accordingly, there is a need for a method for preparing a carbon nanotube heat conducting sheet, which is simple and can improve the heat conducting property of the prepared carbon nanotube heat conducting sheet.
A preparation method of a carbon nano tube heat conducting fin is characterized by comprising the following steps:
forming an oriented carbon nanotube array on a substrate, wherein the substrate is provided with a growth surface and a glue filling surface which are arranged oppositely, the carbon nanotube array is positioned on the growth surface, a plurality of micropores are arranged on the substrate at regular intervals, the micropores are through holes and used for filling raw materials of thermosetting polymer materials, and each carbon nanotube in the carbon nanotube array is provided with a near end close to the growth surface and a free end far away from the growth surface;
injecting glue on the glue injection surface to enable the raw material of the thermosetting polymer material to flow towards the direction close to the free ends of the carbon nano tubes through the micropores so as to fill gaps among the plurality of carbon nano tubes of the carbon nano tube array;
when the distance between the raw material of the thermosetting polymer material flowing along the carbon nano tube and the free end of the carbon nano tube is 0.02 mm-0.2 mm, stopping injecting glue and turning over the substrate to stop the further flow of the raw material of the thermosetting polymer material towards the direction close to the free end of the carbon nano tube;
curing the raw materials of the thermosetting polymer material positioned between the carbon nano tubes to obtain a cured carbon nano tube array; and
and separating the cured carbon nanotube array from the substrate to obtain the carbon nanotube heat-conducting fin.
In order to increase the mechanical strength of the carbon nanotube array, help maintain the structure of the carbon nanotubes, and prevent the carbon nanotube structure from being damaged during use and affecting the thermal conductivity of the thermal conductive sheet, the conventional method usually comprises immersing the entire carbon nanotube array in the raw material of the thermosetting polymer material or pouring the raw material of the thermosetting polymer material from the free ends of the carbon nanotubes to the carbon nanotube array to fill the gaps between the carbon nanotubes, and then curing to form the carbon nanotube thermal conductive sheet. However, during the dipping or pouring process of the conventional method, the free ends of the carbon nanotubes are easily disordered, which easily causes the oriented structure of the carbon nanotube array to be damaged, and the hollow structure of the free ends of the carbon nanotubes is also easily filled with the raw material of the thermosetting polymer material, so that the heat conduction path formed by the carbon nanotubes is separated from the thermal contact surface by a layer of thermosetting polymer material with relatively large thermal resistance, and the heat conductivity of the heat conduction sheet is reduced.
According to the preparation method of the carbon nano tube heat conducting fin, the substrate with the micropores is adopted, so that the raw material of the liquid thermosetting high polymer material can flow in a directional manner, and the orientation of the carbon nano tube in the prepared carbon nano tube heat conducting fin is stable; and the flow of the raw materials of the thermosetting polymer material to the free end is stopped when the raw materials of the thermosetting polymer material are about to reach the free end of the carbon nano tube, so that the opening of the free end of the carbon nano tube is prevented from being filled by the thermosetting polymer material and the heat conductivity is prevented from being reduced, the contact area of the carbon nano tube heat-conducting strip and a heat source is increased, the contact between the carbon nano tube heat-conducting strip and the heat source is better, and the heat-conducting property of the carbon nano tube heat-conducting strip is improved. In addition, the preparation method of the carbon nano tube heat conducting sheet is simple and convenient, and raw materials are saved.
In one embodiment, the diameter of the micropores is 0.1mm to 0.3 mm; and/or the presence of a catalyst in the reaction mixture,
the hole distance between the adjacent micropores is 0.5 mm-1 mm.
In one embodiment, in the step of forming the aligned carbon nanotube array on the substrate, an included angle between the carbon nanotubes in the carbon nanotube array and the growth surface is 75 ° to 90 °.
In one embodiment, the carbon nanotubes are perpendicular to the growth plane.
In one embodiment, in the step of forming the carbon nanotube array on the substrate, the free ends of the carbon nanotubes are connected to the raw materialThe distance between the long surfaces is 100-1000 μm; and/or the diameter of the carbon nano tube is 8 nm-12 nm; and/or the surface density of the carbon nano tubes in the carbon nano tube array is 10g/m2～30g/m2。
In one embodiment, the material of the substrate is a metal foil; and/or the thickness of the substrate is 10-20 μm.
In one embodiment, the thermosetting polymer material is at least one selected from liquid silicone, fluorinated rubber, epoxy resin and acrylic resin; and/or the presence of a catalyst in the reaction mixture,
the viscosity of the raw material of the thermosetting polymer material is 100cps to 1000 cps.
8. The method for producing a carbon nanotube heat-conducting sheet according to any one of claims 1 to 4 and 6 to 7, wherein the step of forming a carbon nanotube array on a substrate comprises:
forming a catalyst layer on the growth surface of the substrate; and
and forming a carbon nano tube array on the catalyst layer by adopting a chemical vapor deposition method.
In one embodiment, the step of forming the carbon nanotube array on the catalyst layer by using a chemical vapor deposition method includes:
reacting the substrate with the catalyst layer with a gaseous carbon source under the conditions of a protective atmosphere and a temperature of 500-900 ℃.
In one embodiment, after the step of separating the cured carbon nanotube array from the substrate, the method further includes a step of performing a surface treatment on the proximal ends of the carbon nanotubes to expose the proximal ends of the carbon nanotubes from the thermosetting polymer material.
Drawings
Fig. 1 is a flowchart of a method for manufacturing a carbon nanotube thermally conductive sheet according to an embodiment;
fig. 2 is a partial view of a substrate in the method for manufacturing the carbon nanotube thermally conductive sheet shown in fig. 1.
Reference numerals: 10. a carbon nanotube heat-conducting sheet; 110. a substrate; 111. growing the surface; 112. pouring a glue surface; 113. micropores; 120. a carbon nanotube array; 130. a thermosetting polymer material.
Detailed Description
The present invention will now be described more fully hereinafter for purposes of facilitating an understanding thereof, and may be embodied in many different forms and are not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may be present. When the terms "vertical," "horizontal," "left," "right," "upper," "lower," "inner," "outer," "bottom," and the like are used to indicate an orientation or positional relationship, it is for convenience of description only based on the orientation or positional relationship shown in the drawings, and it is not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Referring to fig. 1, an embodiment of the present invention provides a method for preparing a carbon nanotube heat conducting sheet 10, including steps a to e, specifically:
step a: a substrate 110 is provided.
Specifically, referring to fig. 2, the substrate 110 has a growth surface 111 and a glue-filling surface 112 disposed opposite to each other; the growth surface 111 is used for forming the carbon nanotube array 120; the potting surface 112 is used for casting the material of the thermosetting polymer material 130. The substrate 110 is provided with a plurality of micro holes 113 arranged at intervals, and the micro holes 113 are through holes. The micro-holes 113 on the substrate 110 allow the liquid thermosetting polymer material 130 to flow from the glue filling surface 112 to the growth surface 111. In the illustrated embodiment, the micropores 113 are arranged at equal intervals. Of course, in other embodiments, the micro-holes 113 may also be arranged in a non-equidistant manner.
In one embodiment, the material of the substrate 110 is metal. In an alternative specific example, the material of the substrate 110 is copper, stainless steel or aluminum. Of course, in other embodiments, the material of the substrate 110 is not limited to the above, and may be other materials as long as it can provide growth support for preparing the carbon nanotubes.
In the present embodiment, the base 110 has a sheet shape. It is understood that in other embodiments, the shape of the substrate 110 is not limited to a sheet shape, but may be other shapes, such as a block shape.
Specifically, the diameter of the micro-holes 113 is 0.1mm to 0.3 mm. If the diameter of the micro-hole 113 is greater than 0.3mm, the number of carbon nanotubes growing on the substrate 110 is limited, thereby limiting the thermal conductivity of the prepared carbon nanotube thermally conductive sheet 10; if the diameter of the micro-holes 113 is smaller than 0.1mm, it is not favorable for the raw material of the thermosetting polymer material 130 to flow toward the direction close to the free end of the carbon nanotube by gravity and/or capillary action, which affects the permeation of the raw material of the thermosetting polymer material 130. In an alternative specific example, the diameter of the micro-holes 113 is 0.1mm, 0.15mm, 0.2mm, 0.25mm, or 0.3 mm. Further, the diameter of the micro-holes 113 is 0.15mm to 0.25 mm.
Specifically, the hole pitch between the minute holes 113 is 0.5mm to 1 mm. If the hole pitch between the micro holes 113 is greater than 1mm, it cannot be ensured that the raw material of the thermosetting polymer material 130 can completely fill the gaps between the carbon nanotubes; if the hole pitch between the micro holes 113 is smaller than 0.5mm, the density of the carbon nanotubes is limited, and the heat conductivity of the prepared carbon nanotube heat-conducting sheet 10 is affected. In an alternative specific example, the hole pitch between adjacent micro holes 113 is 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.8mm, 0.9mm, or 1 mm. Further, the hole pitch between the adjacent micro holes 113 is 0.6mm to 0.8 mm. Further, the hole pitch between the adjacent micro holes 113 is 0.7mm to 0.8 mm. Of course, it should be noted that the inter-hole distance herein refers to the distance between the centers of the micro-holes 113.
In the illustrated embodiment, the orthogonal projection of the micro-holes 113 on the growth surface 111 is circular. Of course, in other embodiments, the shape of the micro-holes 113 is not limited.
In one embodiment, the substrate 110 is a copper foil, a stainless steel sheet, or an aluminum foil, the diameter of the micro holes 113 is 0.1mm to 0.3mm, and the hole pitch between the micro holes 113 is 0.5mm to 1 mm.
In one embodiment, the substrate 110 has a thickness of 10 μm to 20 μm. Of course, in other embodiments, the thickness of the substrate 110 is not limited to the above, and may be adjusted according to actual requirements.
Step b: an aligned carbon nanotube array 120 is formed on the substrate 110.
Specifically, the aligned carbon nanotube array 120 has a plurality of aligned carbon nanotubes, and the central axes of the carbon nanotubes are parallel to each other. The step of forming the carbon nanotube array 120 on the substrate 110 includes: forming a catalyst layer on the growth surface 111 of the substrate 110; and forming the carbon nanotube array 120 on the catalyst layer by using a chemical vapor deposition method (CVD method).
In one embodiment, a catalyst layer is deposited on growth surface 111 of substrate 110 using magnetron sputtering. The material of the catalyst layer is not particularly limited, and a catalyst commonly used in the art for forming carbon nanotubes, for example, at least one of iron, cobalt, and nickel, may be used. Likewise, the thickness of the catalyst layer is not particularly limited as long as the desired aligned carbon nanotubes can be formed.
In one embodiment, the step of forming the carbon nanotube array 120 on the catalyst layer by using a chemical vapor deposition method includes: the substrate 110 having the catalyst layer is reacted with a gaseous carbon source under a protective atmosphere at a temperature of 500 to 900 ℃. Under the conditions of protective atmosphere and 500-900 ℃, the substrate 110 with the catalyst layer reacts with gaseous carbon source, so that the carbon nanotube grows along the growth surface 111 vertical to the substrate 110, has a good orientation structure, and is stably connected with the growth surface of the substrate through the catalyst. In an alternative embodiment, the carbon source is at least one of acetylene, ethylene, and methane; the time for the substrate 110 having the catalyst layer to react with the gaseous carbon source is 3 to 5 min. It is understood that in other embodiments, the chemical vapor deposition conditions may be adjusted according to the length, density and diameter of the carbon nanotubes to be obtained.
In one embodiment, the carbon nanotubes are at an angle of 75 ° to 90 ° with respect to growth surface 111. In an alternative specific example, the carbon nanotubes are perpendicular to the growth plane 111. Of course, in other embodiments, the included angle between the carbon nanotube and the growth surface 111 is not particularly limited, and may be adjusted according to actual needs.
Specifically, each carbon nanotube in the carbon nanotube array 120 has a proximal end near the growth face 111 and a free end away from the growth face 111. In one embodiment, the distance from the free end of the carbon nanotube to the growth surface 111 is 100 μm to 1000 μm. Furthermore, the distance from the free end of the carbon nanotube to the growth surface 111 is 500 μm to 1000 μm. It is understood that in other embodiments, the distance from the free end of the carbon nanotube to the growth surface 111 is not limited to the above, and may be adjusted according to actual requirements.
In one embodiment, the carbon nanotubes in the carbon nanotube array 120 have a diameter of 8nm to 12 nm. When the diameter of the carbon nano tube is 8 nm-12 nm, the regular shape and good orientation of the carbon nano tube array can be ensured, and the uniform heat conduction of the carbon nano tube heat conducting sheet is facilitated. Further, the diameter of the carbon nanotube is 8nm to 10 nm. It is understood that in other embodiments, the diameter of the carbon nanotube is not limited to the above, and may be adjusted according to actual requirements.
In one embodiment, the area density of the carbon nanotubes in the carbon nanotube array 120 is 10g/m2～30g/m2. Carbon in the carbon nanotube array 120The surface density of the nanotubes was 10g/m2～30g/m2In this case, the carbon nanotube array can be ensured to have good thermal conductivity. Further, the surface density of the carbon nanotubes in the carbon nanotube array 120 is 15g/m2～20g/m2. It is understood that in other embodiments, the areal density of the carbon nanotubes is not limited to the above, and can be adjusted according to actual needs.
Step c: and (6) pouring glue.
Specifically, glue is injected on the glue injection surface 112, so that the raw material of the thermosetting polymer material 130 flows through the micro-holes 113 in a direction close to the free ends of the carbon nanotubes, so as to fill gaps between the plurality of carbon nanotubes of the carbon nanotube array 120; when the distance between the raw material of the thermosetting polymer material 130 flowing along the carbon nanotube and the free end of the carbon nanotube is 0.02 mm-0.2 mm, stopping injecting the glue and turning over the substrate 110 to stop the further flow of the raw material of the thermosetting polymer material 130 to the direction close to the free end of the carbon nanotube.
The raw material of the thermosetting polymer material 130 is poured into the carbon nanotube array 120 through the micro-holes 113 on the substrate 110, and the raw material of the thermosetting polymer material 130 flows from the glue pouring surface 112 to a direction close to the free end of the carbon nanotube by using gravity and/or capillary force, so that the carbon nanotube easily maintains its original orientation and is not easily disordered due to the addition of the raw material of the thermosetting polymer material 130. Moreover, the carbon nanotubes are hollow structures, and the flow of the raw material of the thermosetting polymer material 130 to the free end is terminated when the raw material of the carbon nanotubes reaches the free end, so that the opening of the free end is prevented from being filled with the thermosetting polymer material 130, and the heat conducting path formed by the carbon nanotubes and the heat source are separated by the thermosetting polymer material 130, so that the heat conducting performance is reduced. In addition, since the flow of the raw material of the thermosetting polymer material 130 to the free end is terminated when the raw material is about to reach the free end of the carbon nanotube, the contact area of the carbon nanotube heat conducting sheet 10 with the heat source is larger and the contact with the heat source is better when the carbon nanotube heat conducting sheet is applied, and the heat conducting performance of the carbon nanotube heat conducting sheet 10 is improved.
In the present embodiment, each carbon nanotube in the carbon nanotube array 120 is grown in a direction perpendicular to the growth surface 111. At this time, the substrate 110 with the carbon nanotube array 120 is horizontally inverted, wherein the glue filling surface 112 faces upwards, and the growth surface 111 with the carbon nanotube array 120 faces downwards; then, the raw material of the liquid thermosetting polymer material 130 is placed on the potting surface 112, and the raw material of the thermosetting polymer material 130 flows vertically downward through the micro-holes 113 to fill the gaps between the plurality of carbon nanotubes of the carbon nanotube array 120; when the distance between the raw material of the thermosetting polymer material 130 flowing along the carbon nanotube and the free end of the carbon nanotube is 0.02 mm-0.2 mm, stopping injecting the glue and turning the substrate 110 by 180 degrees, so that the growth surface 111 of the substrate 110 faces upwards and the glue injection surface 112 faces downwards, thereby stopping the flow of the raw material of the thermosetting polymer material 130 towards the direction close to the free end of the carbon nanotube. It is understood that in other embodiments, the turning angle is not limited to 180 °, and may be any angle that can terminate the flow of the raw material of the thermosetting polymer material 130 toward the direction close to the free end of the carbon nanotube. Further, when the distance between the raw material of the thermosetting polymer material 130 flowing along the carbon nanotube and the free end of the carbon nanotube is 0.05mm to 0.1mm, the substrate 110 is turned over to terminate the flow of the raw material of the thermosetting polymer material 130 toward the direction close to the free end of the carbon nanotube.
In one embodiment, the thermosetting polymer material 130 is at least one selected from silicone, fluorinated rubber, epoxy, and acrylic. In an alternative specific example, the thermosetting polymer material 130 is at least one of liquid silicone rubber and fluorinated rubber with good mechanical impact resistance. In another alternative specific example, the thermosetting polymer material 130 is at least one of epoxy resin and acrylic resin having strong adhesion. It is understood that in other embodiments, the thermosetting polymer material 130 is not limited to the above, and may be selected according to actual needs.
Of course, the raw material of the thermosetting polymer material 130 corresponds to the thermosetting polymer material 130 to be prepared. In one embodiment, the raw materials of the thermosetting polymer material 130 include a precursor of the thermosetting polymer and a curing agent. In one embodiment, the viscosity of the liquid thermosetting polymer material 130 is 100cps to 1000 cps. If the viscosity of the liquid thermosetting polymer material 130 is greater than 1000cps, the penetration of the raw material of the thermosetting polymer material 130 is difficult, which may affect the smooth filling of the raw material of the thermosetting polymer material 130 in the gap between the carbon nanotubes; if the viscosity of the liquid thermosetting polymer material 130 is less than 100cps, it is difficult to control the raw material of the thermosetting polymer material 130 to terminate when it is about to reach the free ends of the carbon nanotubes. Further, the raw material viscosity of the liquid thermosetting polymer material 130 is 200cps to 800 cps.
Step d: curing the raw material of the thermosetting polymer material 130 between the carbon nanotubes to obtain the cured carbon nanotube array 120.
Specifically, after the substrate 110 is turned over so that the flow of the raw material of the thermosetting polymer material 130 toward the direction close to the free ends of the carbon nanotubes is terminated, the raw material of the thermosetting polymer material 130 located between the carbon nanotubes is cured. After the raw material of the thermosetting polymer material 130 between the carbon nanotubes is cured, the thermosetting polymer material 130 and the carbon nanotubes form a cured carbon nanotube array.
In one embodiment, the temperature of curing is 50 ℃ to 150 ℃; the curing time is 10 min-30 min. Further, the curing temperature is 50 ℃ to 100 ℃. Of course, in other embodiments, the curing temperature and time can be adjusted according to the selected property of the raw material of the thermosetting polymer material 130, as long as the raw material of the thermosetting polymer material 130 can be cured without affecting the carbon nanotubes.
Step e: and separating the cured carbon nanotube array 120 from the substrate 110 to obtain the carbon nanotube thermally conductive sheet 10.
Specifically, the method of separating the cured carbon nanotube array 120 from the substrate 110 is not particularly limited, and a method commonly used in the art, such as peeling the substrate 110 from the cured carbon nanotube array 120, may be employed.
In some embodiments, after the step of separating the cured carbon nanotube array 120 from the substrate 110, a step of surface treating the proximal ends of the carbon nanotubes is further included to expose the proximal ends of the carbon nanotubes from the thermosetting polymer material 130. By exposing the proximal end of the carbon nanotube from the thermosetting polymer material 130, the heat conduction between the carbon nanotube heat conducting strip and the heat source can be prevented from being blocked by the thermosetting polymer material with poor heat conduction performance, and meanwhile, the thermal contact resistance between the carbon nanotube heat conducting strip 10 and the heat source is smaller and better in contact with the heat source when the carbon nanotube heat conducting strip is applied, so that the heat conduction performance of the carbon nanotube is improved.
Specifically, the surface treatment method is at least one selected from plasma etching, chemical modification and metal deposition.
In the preparation method of the carbon nanotube heat conduction sheet 10, the substrate 110 with the micropores 113 is adopted, so that the orientation of the carbon nanotubes in the prepared carbon nanotube heat conduction sheet 10 is stable; the preparation method also stops the flow of the raw material of the thermosetting polymer material 130 to the free end when the raw material of the thermosetting polymer material 130 is about to reach the free end of the carbon nano tube, so that the opening of the free end of the carbon nano tube is prevented from being filled by the thermosetting polymer material 130 to reduce the heat conductivity, the contact area of the carbon nano tube heat-conducting strip 10 and a heat source is increased, the contact of the carbon nano tube heat-conducting strip 10 and the heat source is better, and the heat-conducting performance of the carbon nano tube heat-conducting strip 10 is improved.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The following detailed description is given with reference to specific examples. The following examples are not specifically described, and other components except inevitable impurities are not included. The examples, which are not specifically illustrated, employ drugs and equipment, all of which are conventional in the art. The experimental procedures, in which specific conditions are not indicated in the examples, were carried out according to conventional conditions, such as those described in the literature, in books, or as recommended by the manufacturer.
Example 1
(1) Providing a copper foil substrate, wherein the substrate is provided with a growth surface and a glue pouring surface opposite to the growth surface, a plurality of spaced micropores are distributed on the copper foil substrate, the diameter of each micropore is 0.2mm, and the distance between every two micropores is 0.8 mm.
(2) And depositing 20nm of iron as a catalyst layer on the growth surface of the copper foil substrate by a magnetron sputtering method.
(3) Heating the copper foil substrate with the catalyst layer to 700 ℃ in a protective gas environment, introducing acetylene to react for 3.5min to obtain the vertically grown carbon nanotube array with a good oriented structure. The carbon nanotube has a proximal end and a free end, the proximal end being proximal to the growth face and the free end being distal to the growth face. The length of the carbon nano tube is 340 mu m, the diameter of the carbon nano tube is 10nm, and the density of the carbon nano tube in the carbon nano tube array is 15g/m2。
(3) Inverting the copper foil substrate with the carbon nanotube array, namely, the glue filling surface of the copper foil substrate is upward, the growth surface of the copper foil substrate is downward, the carbon nanotube array is below the copper foil substrate, and the extension direction of the carbon nanotube is vertical to the horizontal plane; then slowly dripping liquid silica gel (HY 9300, Hongyeje technology Limited, Shenzhen) with a dropper above the copper foil substrate, wherein the viscosity of the liquid silica gel is 800cps, and when the distance between the liquid silica gel flowing along the carbon nano tube and the free end of the carbon nano tube is 0.2mm, turning over the copper foil substrate to ensure that the gel filling surface of the copper foil substrate faces downwards, the growth surface of the copper foil substrate faces upwards, and the carbon nano tube array is above the copper foil substrate; followed by curing at 80 ℃ for 20 min. After the curing, the carbon nanotube array after the curing was separated from the copper foil substrate, and the carbon nanotube thermally conductive sheet of example 1 was obtained.
Example 2
The carbon nanotube thermally conductive sheet of example 2 was produced in substantially the same manner as in example 1, except that in example 2, the diameter of the micro holes in the substrate was 0.3mm, and the pitch between the micro holes was 0.5 mm.
Example 3
The carbon nanotube thermally conductive sheet of example 3 was prepared in substantially the same manner as in example 1, except that in example 3, the diameter of the micro holes in the substrate was 0.1mm, and the pitch between the micro holes was 1 mm.
Example 4
The carbon nanotube thermally conductive sheet of example 4 was prepared in substantially the same manner as in example 1, except that in example 4, the growth time of the carbon nanotubes was 4min, and the length of the carbon nanotubes was 500 μm.
Example 5
The carbon nanotube thermally conductive sheet of example 5 was produced in substantially the same manner as in example 1, except that in example 5, the catalyst layer had a thickness of 23nm and the carbon nanotubes had a density of 30g/m2。
Example 6
The carbon nanotube thermally conductive sheet of example 6 was produced in substantially the same manner as in example 1, except that in example 6, the diameter of the micropores in the substrate was 1 mm.
Example 7
The carbon nanotube thermally conductive sheet of example 7 was produced in substantially the same manner as in example 1, except that in example 7, the hole pitch between the micropores in the substrate was 2 mm.
Comparative example 1
The carbon nanotube thermally conductive sheet of comparative example 1 was prepared by the method substantially the same as that of example 1, except that in comparative example 1, step (3) was:
and (3) normally placing the micropores with the carbon nanotube arrays, namely, the glue filling surface of the copper foil substrate faces downwards, the growth surface of the copper foil substrate faces upwards, the carbon nanotube arrays are arranged above the copper foil substrate, and the extension directions of the carbon nanotubes are vertical to the horizontal plane. Then, slowly dripping liquid silica gel above the carbon nanotube array by using a dropper, and after the carbon nanotube array is completely soaked by the silica gel, sucking residual liquid silica gel on the surface of the carbon nanotube array by using filter paper; then cured at 80 ℃ for 20 min. And after the solidification is finished, separating the solidified carbon nanotube array from the copper foil substrate to obtain the carbon nanotube heat-conducting sheet of the comparative example 1.
Testing
The thermal conductivity of the carbon nanotube thermally conductive sheets of each example and comparative example was measured using the standard ASTM D5470, and the results are shown in table 1:
TABLE 1
As can be seen from table 1, the thermal conductivity of the carbon nanotube thermally conductive sheets of examples 1 to 4 is higher than that of the carbon nanotube thermally conductive sheet of comparative example 1. As can be seen from example 5, when the diameter of the micropores of the substrate is too large, it is not favorable to control the flow rate of the thermosetting polymer material, and it is not easy to improve the thermal conductivity of the carbon nanotube thermally conductive sheet. As can be seen from example 6, when the distance between the micropores of the substrate is relatively large (the micropores are relatively sparse), it is not favorable for the thermosetting polymer material to fully impregnate the carbon nanotube array.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A preparation method of a carbon nano tube heat conducting fin is characterized by comprising the following steps:
forming an oriented carbon nanotube array on a substrate, wherein the substrate is provided with a growth surface and a glue filling surface which are arranged oppositely, the carbon nanotube array is positioned on the growth surface, a plurality of micropores are arranged on the substrate at regular intervals, the micropores are through holes and used for filling raw materials of thermosetting polymer materials, and each carbon nanotube in the carbon nanotube array is provided with a near end close to the growth surface and a free end far away from the growth surface;
injecting glue on the glue injection surface so that the raw material of the thermosetting polymer material flows towards the direction close to the free ends of the carbon nano tubes through the micropores to fill gaps among the plurality of carbon nano tubes of the carbon nano tube array;
when the distance between the raw material of the thermosetting polymer material flowing along the carbon nano tube and the free end of the carbon nano tube is 0.02 mm-0.2 mm, stopping injecting glue and turning over the substrate to stop the further flow of the raw material of the thermosetting polymer material towards the direction close to the free end of the carbon nano tube;
curing the raw materials of the thermosetting polymer material positioned between the carbon nano tubes to obtain a cured carbon nano tube array; and
and separating the cured carbon nanotube array from the substrate to obtain the carbon nanotube heat-conducting fin.
2. The method for producing a carbon nanotube thermally conductive sheet according to claim 1, wherein the diameter of the micro-hole is 0.1mm to 0.3 mm; and/or the presence of a catalyst in the reaction mixture,
the hole distance between the adjacent micropores is 0.5 mm-1 mm.
3. The method according to claim 1, wherein in the step of forming the aligned carbon nanotube array on the substrate, the carbon nanotubes in the carbon nanotube array have an angle of 75 ° to 90 ° with respect to the growth surface.
4. The method according to claim 3, wherein the carbon nanotubes are perpendicular to the growth surface.
5. The method of producing a carbon nanotube heat-conducting sheet according to any one of claims 1 to 4, wherein in the step of forming a carbon nanotube array on a substrate, the distance from the free end of the carbon nanotube to the growth surface is 100 μm to 1000 μm; and/or the diameter of the carbon nano tube is 8 nm-12 nm; and/or the surface density of the carbon nano tubes in the carbon nano tube array is 10g/m2～30g/m2。
6. The method for producing a carbon nanotube thermally conductive sheet according to claim 1, wherein the substrate is made of a metal foil; and/or the thickness of the substrate is 10-20 μm.
7. The method according to claim 1, wherein the thermosetting polymer material is at least one selected from liquid silicone, fluorinated rubber, epoxy resin, and acrylic resin; and/or the presence of a catalyst in the reaction mixture,
the viscosity of the raw material of the thermosetting polymer material is 100cps to 1000 cps.
8. The method for producing a carbon nanotube heat-conducting sheet according to any one of claims 1 to 4 and 6 to 7, wherein the step of forming a carbon nanotube array on a substrate comprises:
forming a catalyst layer on the growth surface of the substrate; and
and forming a carbon nano tube array on the catalyst layer by adopting a chemical vapor deposition method.
9. The method of claim 8, wherein the step of forming the carbon nanotube array on the catalyst layer by chemical vapor deposition comprises:
reacting the substrate with the catalyst layer with a gaseous carbon source under the conditions of a protective atmosphere and a temperature of 500-900 ℃.
10. The method according to claim 1, further comprising a step of surface-treating the proximal ends of the carbon nanotubes to expose the proximal ends of the carbon nanotubes from the thermosetting polymer material after the step of separating the cured carbon nanotube array from the substrate.
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