Coating with High Infrared Emissivity and Strong Binding Force on the Surface of Carbon / Carbon Composite Material, Preparation Method and Application

Abstract

The present invention discloses a coating with high infrared emissivity and strong bonding force on the surface of a carbon / carbon composite material, its preparation method and application, which relates to the technical field of infrared radiation coating materials. The coating components and the mass fractions of each component are as follows: 22-26 parts of carbon nanotubes, 6-8 parts of carbon nanotube dispersant, 15-20 parts of nano carbon black, 3-5 parts of phenolic resin, 8-11 parts of urea, and 5000-6100 parts of isopropanol. By applying carbon nanotubes and using the foaming effect of urea for pore regulation, the present invention is beneficial to reducing the areal density of the coating, and better weight reduction benefits can be obtained. Moreover, raw materials with low prices are selected as the main materials of the coating, the composition of the coating is optimized, and an infrared high-emissivity coating with good interfacial bonding with the carbon / carbon composite material and excellent thermal shock resistance is prepared through a simple preparation process.

Description

Technical Field

[0001] The present invention relates to the technical field of infrared radiation coating materials, and particularly relates to a coating with high infrared emissivity and strong bonding force on the surface of a carbon / carbon composite material, and a preparation method and application thereof. Background Art

[0002] In the future, high-power spacecraft thermal control systems urgently need lightweight, high-temperature resistant, high-thermal conductivity, and high-heat dissipation materials. Carbon / carbon (C / C) composite materials have characteristics such as low density, high strength, and excellent temperature resistance, and have become important candidates for the development of new spacecraft thermal control systems. Thanks to the breakthrough and application of high-thermal conductivity mesophase pitch fiber and high-thermal conductivity carbon matrix preparation technologies, the thermal conductivity of C / C composite materials can reach 600-900 W / (m·K). However, the improvement of thermal conductivity is inevitably accompanied by the low porosity and large and complete graphite sheet layer structure of C / C composite materials, resulting in poor surface radiation heat dissipation ability. The surface heat cannot be dissipated in time, which easily leads to uneven distribution of thermal stress in the components and failure. Therefore, to further improve the thermal control ability of C / C composite materials, preparing a high-infrared emissivity heat dissipation coating on the surface of high-thermal conductivity C / C composite materials can achieve the "conducting and dissipating" thermal control effect.

[0003] Based on the principle of matching of thermophysical properties, carbonaceous materials are mostly selected for the high-infrared emission coating on the surface of C / C composite materials. For example, vertical graphene coatings are grown on the surface of C / C composite materials using CVD technology. Although the graphene coatings have optical blackness, their infrared emissivity is only 0.78; or CNTs arrays are prepared on a smooth surface, and their emissivity can reach 0.98-0.99 in the range of 0.2-200 μm, approaching the blackbody level. However, the preparation stability of CNTs coatings is poor and it is difficult to scale up. Therefore, a carbon black coating with excellent interfacial bonding and high infrared emissivity is constructed on the surface of C / C composite materials using commercial nanocarbon black as the raw material and by means of compressed air spraying technology. However, a single-component pure carbon black material still has the limitation of insufficient coating toughness, and the carbon black spheres with nanoscale on the surface of the composite material are too closely packed, resulting in small pores (pore diameter 20-100 nm). During the subsequent CVI pyrolytic carbon reinforcement coating process, the pyrolytic carbon is extremely easy to fill the pores, ultimately leading to a decrease in infrared emissivity (less than 0.9). To solve this problem, those skilled in the art often reduce the pyrolytic carbon deposition amount, but this measure will greatly weaken the bonding between the coating and the substrate. Therefore, optimizing and regulating the components and pore size of the carbon coating to obtain high infrared emissivity and strong coating bonding force during the CVI deposition and pyrolytic carbon reinforcement process is a technical problem that urgently needs to be broken through in this field.

[0004] In summary, it has become the focus and difficulty of current research work to prepare a composite coating with an appropriate pore structure and enhanced by synergistic multi-phase carbon nanomaterials on the surface of carbon / carbon composites to achieve the integration goal of high emissivity, good interfacial bonding, and excellent thermal shock resistance. And based on practical applications, the spraying method is often used for coating preparation due to its simple process. However, many influencing factors during spraying make its process stability poor. Therefore, exploring a method to actively regulate the microstructure of the coating to improve the stability of the spraying process is an urgent problem to be clarified currently. Summary of the Invention

[0005] To solve the deficiencies in the above-mentioned background technology, mainly aiming at the problem that it is difficult to achieve both high infrared emissivity and high bonding strength due to CVI pyrolytic carbon deposition in the early carbon black coating, and the problem of insufficient structural strength of single carbon black nanoparticles. The present invention provides a coating with high infrared emissivity and strong bonding force on the surface of carbon / carbon composites, its preparation method and application. The coating uses carbon black as the base material and adds a reinforcing phase of commercial carbon nanotubes (CNTs) with a one-dimensional morphology to solve the problem of insufficient structural strength of single carbon black nanoparticles. At the same time, urea is added to the coating slurry, and by virtue of its pyrolytic foaming characteristics, the distribution of carbon black and carbon nanotubes is optimized and regulated to construct a pore structure with optimized size, thereby providing conditions for depositing a larger amount of pyrolytic carbon by CVI for a long time, and finally solving the problem that it is difficult to achieve both high infrared emissivity and high bonding strength due to CVI pyrolytic carbon deposition in the early carbon black coating. In addition, the CNTs adopted in the present invention and the use of urea as a foaming agent to reflect pore regulation are beneficial to reducing the areal density of the coating and can achieve better weight reduction benefits. The coating prepared by the method provided by the present invention has the characteristics of high emissivity, excellent thermal shock resistance, low cost, and simple preparation process, enabling the thermal management ability of carbon / carbon composites to meet the requirements of heat dissipation components.

[0006] To achieve the above object, the first object of the present invention provides a coating with high infrared emissivity and strong bonding force on the surface of carbon / carbon composites. The coating components and the mass fractions of each component are: 22 - 26 parts of carbon nanotubes, 6 - 8 parts of carbon nanotube dispersant, 15 - 20 parts of nano carbon black, 3 - 5 parts of phenolic resin, 8 - 11 parts of urea, and 5000 - 6100 parts of isopropanol.

[0007] Preferably, the coating components and the mass fractions of each component are: 26 parts of carbon nanotubes, 8 parts of carbon nanotube dispersant, 16 parts of nano carbon black, 5 parts of phenolic resin, 8 parts of urea, and 6022 parts of isopropanol.

[0008] Preferably, the carbon nanotube dispersant is carbon nanotube alcohol dispersant TNADIS.

[0009] Preferably, a pyrolytic carbon layer is further provided on the coating.

[0010] The second object of the present invention is to provide a method for preparing a coating with high infrared emissivity and strong bonding force on the surface of a carbon / carbon composite material, comprising the following steps:

[0011] Disperse phenolic resin into 20-25 parts by mass of isopropyl alcohol to obtain a phenolic resin solution;

[0012] Add a carbon nanotube dispersant to carbon nanotubes, then add the remaining isopropyl alcohol for dilution to obtain a carbon nanotube solution; uniformly disperse nano carbon black in the carbon nanotube solution to obtain a mixed solution;

[0013] Add the phenolic resin solution to the mixed solution, and add urea, then mix evenly to obtain a coating slurry;

[0014] Coat the coating slurry on the surface of the carbon / carbon composite material, and after heat treatment, a coating with high infrared emissivity and strong bonding force on the surface of the carbon / carbon composite material is obtained.

[0015] Preferably, after heat treatment, it further includes: under the condition that the gas flow ratio of methane to argon is 1:4-5, pyrolytic deposition is carried out to obtain a pyrolytic carbon layer deposited on the coating with high infrared emissivity and strong bonding force on the surface of the carbon / carbon composite material.

[0016] More preferably, the pyrolytic deposition temperature is 1060-1080 °C, and the deposition time is 15-30 min.

[0017] Preferably, during the heat treatment process, it includes: slowly heating to 150-160 °C at a rate of 4-5 °C / min in an air atmosphere and holding for 5 min.

[0018] Preferably, during the process of coating the coating slurry on the surface of the carbon / carbon composite material, it includes:

[0019] Spray the coating slurry onto the surface of the carbon / carbon composite material with a spray gun. When spraying, the outlet of the spray gun forms an angle of 45-60 degrees with the surface of the carbon / carbon composite material, the distance between the outlet of the spray gun and the surface of the carbon / carbon composite material is 5-9 cm, and each part of the material surface is sprayed several times until the surface of the carbon / carbon composite material is completely and evenly covered by the slurry.

[0020] The third object of the present invention is to provide an application of the coating in a carbon / carbon composite material.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] The present invention relates to a coating with high infrared emissivity on the surface of a carbon / carbon composite material and a preparation method thereof. Low-cost commercial raw materials are selected as the main materials of the coating, the composition of the coating is optimized, and an infrared high-emissivity coating with good interfacial bonding with the carbon / carbon composite material and excellent thermal shock resistance is prepared through a simple preparation process.

[0023] Taking advantage of the characteristic that the decomposition temperature of urea is equivalent to the softening temperature of phenolic resin, after being treated by a suitable spraying process and an appropriate heat treatment process, urea decomposes to release a large amount of gas when the phenolic resin softens. The release of these gases can construct a uniform nano-network structure on the coating surface with carbon nanotubes as the skeleton and nano-carbon black as the high-emissivity filler, while maintaining the performance stability with high emissivity. After depositing a certain amount of pyrolytic carbon as the matrix of the composite coating to reinforce the coating, the interfaces between carbon nanotubes bond and pull each other, and the elastic network formed by them endows it with excellent thermal shock resistance. The beneficial effects of the present invention are as follows:

[0024] (1) After adding urea to the slurry, the coating is pyrolytically foamed to adjust the distribution of nano-carbon black and carbon nanotubes on the surface, forming a large number of network structures with nanoscale pores on the coating surface, which is beneficial to the deposition of CVI trace pyrolytic carbon, improves the interfacial bonding strength, and alleviates the problem of pore sealing caused during the deposition of pyrolytic carbon. The areal density is reduced from 0.05 kg / m 2 to 0.03 kg / m 2 ; at the same time, it effectively solves the problem of large deviation in emissivity results caused by particle agglomeration during large-scale preparation, greatly improves the stability of the spraying process, and the average emissivity in the 1 - 22 μm band can reach 0.97, and the result floating value is within 0.01.

[0025] (2) The coating is a composite coating composed of two carbon nanomaterials. The high specific surface area of nano-carbon black can provide more interfaces and sites for the scattering and absorption of infrared rays, greatly improving the infrared emissivity; carbon nanotubes themselves are also good electromagnetic wave absorbers, and their excellent micro-mechanical properties can also provide considerable toughness for the coating. The highest emissivity that can be achieved is 0.98 in the 1 - 22 μm band. According to the actual application situation of the coating, the performance of the coating can be adjusted by adjusting the proportion of the two nano-materials in the coating within a certain range.

[0026] (3) The raw material of the coating and the matrix carbon / carbon composite material are both carbon materials. After depositing pyrolytic carbon, good interfacial bonding can be achieved between the two. The carbon nanotubes in the composite coating are also strengthened and bonded by the pyrolytic carbon layer to form an elastic network, thereby buffering the thermal stress from the carbon / carbon composite material and effectively solving the problems of cracking and peeling of the coating under the thermal shock conditions of rapid temperature change. According to the actual requirements of the coating, adjust the deposition parameters of pyrolytic carbon to control the deposition amount of pyrolytic carbon. After 60 thermal cycles of 300°C ↔ -196°C, no cracking phenomenon occurs, and the emissivity is higher than 0.90. Description of the Drawings

[0027] Figure 1 It is the scanning electron microscope photograph after the spraying coating step of Example 1.

[0028] Figure 2 It is the scanning electron microscope photograph of the coating after the heat treatment step in Example 1.

[0029] Figure 3 It is the scanning electron microscope photograph after the pyrolytic carbon deposition step for 15 min in Example 1.

[0030] Figure 4 It is the mechanical property of the scratch test of the coating before and after the pyrolytic carbon deposition in Example 1.

[0031] Figure 5 It is the microscopic morphology of the carbon black coating after the pyrolytic carbon deposition in Comparative Example 1.

[0032] Figure 6 It is the scanning electron microscope images before (a) and after (b) the pyrolytic carbon deposition when urea is not added. Detailed implementation manners

[0033] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention will be further described below in conjunction with specific embodiments and drawings, but the exemplified embodiments shall not be construed as limiting the present invention.

[0034] The present invention provides a coating with high infrared emissivity and strong bonding force on the surface of a carbon / carbon composite material. The coating components and the mass fractions of each component are as follows: 22-26 parts of carbon nanotubes, 6-8 parts of carbon nanotube dispersant, 15-20 parts of nano carbon black, 3-5 parts of phenolic resin, 8-11 parts of urea, and 5000-6100 parts of isopropanol.

[0035] Preferably, the coating components and the mass fractions of each component are as follows: 26 parts of carbon nanotubes, 8 parts of carbon nanotube dispersant, 16 parts of nano carbon black, 5 parts of phenolic resin, 8 parts of urea, and 6022 parts of isopropanol.

[0036] The present invention utilizes the characteristic that the decomposition temperature of urea is equivalent to the softening temperature of phenolic resin. After being treated by a suitable spraying process and an appropriate heat treatment process, a large amount of gas is released when urea decomposes at the softening of phenolic resin. The release of these gases can construct a uniform nano-network structure with carbon nanotubes as the skeleton and nano carbon black as the high-emissivity filler on the coating surface, while maintaining the stability of performance while having high emissivity.

[0037] Among them, the carbon nanotube dispersant

[0038] The nano carbon black is spherical particles with a diameter of 15 nm.

[0039] The outer diameter of the carbon nanotubes is 30-80 nm, and the length is <10 μm.

[0040] According to the present invention, a pyrolytic carbon layer is further provided on the coating. After depositing a certain amount of pyrolytic carbon as the matrix of the composite coating to reinforce the coating, the interfaces between carbon nanotubes are bonded and traction to each other, and the elastic network formed by them endows it with excellent thermal shock resistance.

[0041] The present invention provides a method for preparing a coating with high infrared emissivity and strong bonding force on the surface of a carbon / carbon composite material, comprising the following steps:

[0042] Disperse phenolic resin into 20 - 25 parts by mass of isopropyl alcohol to obtain a phenolic resin solution;

[0043] Add a carbon nanotube dispersant to carbon nanotubes, and then add the remaining isopropyl alcohol for dilution to obtain a carbon nanotube solution; uniformly disperse nano carbon black in the carbon nanotube solution to obtain a mixed solution;

[0044] Add the phenolic resin solution to the mixed solution, and add urea, then mix evenly to obtain a coating slurry;

[0045] Coat the coating slurry on the surface of the carbon / carbon composite material, and after heat treatment, a coating with high infrared emissivity and strong bonding force on the surface of the carbon / carbon composite material is obtained.

[0046] In the present invention, after adding urea to the slurry, the coating is pyrolytically foamed to adjust the distribution of nano carbon black and carbon nanotubes on the surface, and a network structure with a large number of nano-scale pores is formed on the coating surface, as Figure 2 shown, which is beneficial to the deposition of CVI trace pyrolytic carbon, improves the interface bonding strength, and compared with Figure 3 and Figure 5 it can be seen that the problem of pore sealing caused during the deposition of pyrolytic carbon is alleviated.

[0047] According to the present invention, after heat treatment, it further includes: under the condition that the gas flow ratio of methane to argon is 1:4 - 5, pyrolytic deposition is carried out to obtain a pyrolytic carbon layer deposited on the coating with high infrared emissivity and strong bonding force on the surface of the carbon / carbon composite material.

[0048] In the present invention, a pyrolytic carbon layer is deposited on the coating to form a composite coating composed of two carbon nanomaterials. The high specific surface area of nano carbon black can provide more interfaces and sites for the scattering and absorption of infrared rays, greatly improving the infrared emissivity; carbon nanotubes themselves are also good electromagnetic wave absorbers, and their excellent micro-mechanical properties can also provide considerable toughness for the coating. The raw material of the coating and the matrix carbon / carbon composite material are both carbon materials, and after depositing pyrolytic carbon, good interface bonding can be achieved between the two. The carbon nanotubes in the composite coating are also strengthened and bonded by the pyrolytic carbon layer to form an elastic network, thereby buffering the thermal stress from the carbon / carbon composite material and effectively solving the problems of cracking and peeling of the coating under thermal shock conditions with rapid temperature changes.

[0049] Wherein, the pyrolysis deposition temperature is 1060-1080°C, and the deposition time is 15-30min.

[0050] The heat treatment process includes: slowly heating to 150-160°C at 4-5°C / min in an air atmosphere and keeping the temperature for 5 minutes.

[0051] The process of applying the coating slurry to the surface of the carbon / carbon composite material includes:

[0052] Spray the coating slurry onto the surface of the carbon / carbon composite material with a spray gun. When spraying, it must be noted that the discharge port is at an angle of 45-60 degrees to the surface of the carbon / carbon composite material, and the distance between the discharge port and the surface of the carbon / carbon composite material is 5-9 cm. Spray the surface of the material several times until the surface of the carbon / carbon composite material is completely and evenly covered with the slurry.

[0053] The invention provides application of a coating in a carbon / carbon composite material.

[0054] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0055] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0056] Example 1

[0057] A coating with high infrared emissivity and strong bonding ability on the surface of a carbon / carbon composite material is prepared by the following method:

[0058] (1) Add 5 parts by mass of phenolic resin to 25 parts by mass of isopropanol and thoroughly sonicate until completely dissolved, and then set aside to obtain a phenolic resin isopropanol solution; add 8 parts by mass of carbon nanotube dispersant to 25 parts by mass of carbon nanotubes, add 5500 parts by mass of isopropanol to dilute, and then sonicate for 20 minutes to evenly disperse; then add nano carbon black in portions of 5 parts by mass each time, and sonicate for 5 minutes before adding the next time, adding a total of 15 parts by mass. When the obtained slurry is shaken, there should be no obvious agglomerated particles on the inner wall of the beaker, and a dispersed slurry is obtained; add 25 parts by mass of phenolic resin isopropanol solution to the dispersed slurry, and then sonicate for 5 minutes; add 8 parts by mass of urea and sonicate for 5 minutes, and finally obtain a coating slurry.

[0059] (2) Use compressed air spraying technology and spray the carbon / carbon composite material surface with a spray gun. When spraying, pay attention to the angle of 55 degrees between the discharge port and the surface of the carbon / carbon composite material. The distance between the discharge port and the surface of the carbon / carbon composite material is 7 cm. Spray the surface of the material several times until the surface of the carbon / carbon composite material is completely and evenly covered with slurry.

[0060] (3) To improve the stability of the spraying process, the prepared material was slowly heated to 160°C at 5°C / min in an air atmosphere and kept warm for 5 min.

[0061] (4) In order to improve the bonding strength between the coating and the surface of the carbon / carbon composite material in practical applications, pyrolytic carbon was deposited using a chemical vapor deposition process at 1060°C with a methane to argon gas flow ratio of 1:4 for 15 min.

[0062] The prepared high infrared emissivity coating has an average emissivity of 0.968 in the 1-22 μm band; after the pyrolytic carbon layer is deposited, the average emissivity in the 1-22 μm band is 0.952, the floating values are all within 0.01, and the scratch destructive force of the coating is 22.1 N. The coating described in this embodiment has no cracking after 60 thermal cycles at 300°C↔-196°C.

[0063] Example 2

[0064] A coating with high infrared emissivity and strong bonding ability on the surface of a carbon / carbon composite material is prepared by the following method:

[0065] (1) Add 3 parts by mass of phenolic resin to 25 parts by mass of isopropanol and thoroughly sonicate until completely dissolved, and then set aside to obtain a phenolic resin isopropanol solution; add 6 parts by mass of carbon nanotube dispersant to 22 parts by mass of carbon nanotubes, add 5000 parts by mass of isopropanol to dilute, and then sonicate for 20 minutes to evenly disperse; then add nano carbon black in portions of 3 parts by mass each time, and sonicate for 5 minutes before adding the next time, adding a total of 18 parts by mass. When the obtained slurry is shaken, there should be no obvious agglomerated particles on the inner wall of the beaker, and a dispersed slurry is obtained; add 25 parts by mass of phenolic resin isopropanol solution to the dispersed slurry, and then sonicate for 5 minutes; add 9 parts by mass of urea and sonicate for 5 minutes, and finally obtain a coating slurry.

[0066] (2) Use compressed air spraying technology and spray the carbon / carbon composite material surface with a spray gun. When spraying, pay attention to the angle of 50 degrees between the discharge port and the surface of the carbon / carbon composite material. The distance between the discharge port and the surface of the carbon / carbon composite material is 5-9 cm. Spray the surface of the material several times until the surface of the carbon / carbon composite material is completely and evenly covered with slurry.

[0067] (3) To improve the stability of the spraying process, the prepared material was slowly heated to 155 °C at a rate of 4 °C / min in an air atmosphere and held for 5 min.

[0068] (4) To improve the bonding strength between the coating and the surface of the carbon / carbon composite material during actual application, pyrolytic carbon was deposited using chemical vapor deposition at 1070 °C with a methane to argon gas flow ratio of 1:5, and the time was controlled to be 20 min as needed.

[0069] The average emissivity of the prepared high-infrared emissivity coating in the 1 - 22 μm band was 0.959; after depositing the pyrolytic carbon layer, the average emissivity in the 1 - 22 μm band was 0.941, and the floating values were all within 0.01. The scratch destructive force of the coating was 23.6 N. The coating described in this example showed no cracking after 60 thermal cycles of 300 °C ↔ -196 °C.

[0070] Example 3

[0071] A coating with high infrared emissivity and strong bonding ability on the surface of a carbon / carbon composite material was prepared by the following method:

[0072] (1) 5 parts by mass of phenolic resin was added to 22 parts by mass of isopropanol and ultrasonically treated until completely dissolved for later use, obtaining a phenolic resin isopropanol solution.

[0073] 8 parts by mass of a carbon nanotube dispersant was added to 26 parts by mass of carbon nanotubes, diluted with 6000 parts by mass of isopropanol, and ultrasonically dispersed for 20 min to be uniformly dispersed.

[0074] Then, 16 parts by mass of nano carbon black was added in portions of 4 parts by mass each time. After ultrasonic treatment for 5 min each time, the next addition was made. When the obtained slurry was shaken, there should be no obvious agglomerated particles on the inner wall of the beaker, obtaining a dispersed slurry.

[0075] 22 parts by mass of the phenolic resin isopropanol solution was added to the dispersed slurry and then ultrasonically treated for 5 min; 11 parts by mass of urea was added and ultrasonically treated for 5 min, finally obtaining a coating slurry.

[0076] (2) Using a compressed air spraying process, it was sprayed onto the surface of the carbon / carbon composite material with a spray gun. During spraying, it was necessary to note that the outlet of the spray gun was at a 60-degree angle to the surface of the carbon / carbon composite material, and the distance between the outlet of the spray gun and the surface of the carbon / carbon composite material was 9 cm. Each part of the material surface was sprayed several times until the surface of the carbon / carbon composite material was completely and evenly covered with the slurry.

[0077] (3) To improve the stability of the spraying process, the prepared material was slowly heated to 150 °C at a rate of 5 °C / min in an air atmosphere and held for 5 min.

[0078] (4) In order to improve the bonding strength between the coating and the surface of the carbon / carbon composite material in practical applications, pyrolytic carbon was deposited using a chemical vapor deposition process at 1060°C with a methane to argon gas flow ratio of 1:5, and the time was controlled to be 25 min as required.

[0079] The prepared high infrared emissivity coating has an average emissivity of 0.962 in the 1-22 μm band; after the pyrolytic carbon layer is deposited, the average emissivity in the 1-22 μm band is 0.932, the floating values are all within 0.01, and the scratch destructive force of the coating is 26.7 N. The coating described in this embodiment has no cracking after 60 thermal cycles at 300°C↔-196°C.

[0080] Example 4

[0081] A coating with high infrared emissivity and strong bonding ability on the surface of a carbon / carbon composite material is prepared by the following method:

[0082] (1) Add 5 parts by mass of phenolic resin to 25 parts by mass of isopropanol solution and thoroughly sonicate until completely dissolved, and then set aside to obtain a phenolic resin isopropanol solution; add 6 parts by mass of carbon nanotube dispersant to 22 parts by mass of carbon nanotubes, add 5000 parts by mass of isopropanol to dilute, and then sonicate for 20 minutes to evenly disperse; then add nano carbon black in portions of 5 parts by mass each time, and sonicate for 5 minutes before adding the next time, adding a total of 20 parts by mass, and the obtained slurry should have no obvious agglomerated particles on the inner wall of the beaker when shaking, and obtain a dispersed slurry; add 25 parts by mass of phenolic resin isopropanol solution to the dispersed slurry and then sonicate for 5 minutes; add 10 parts by mass of urea and sonicate for 5 minutes, and finally obtain a coating slurry.

[0083] (2) Use compressed air spraying technology and spray the carbon / carbon composite material surface with a spray gun. When spraying, pay attention to the angle of 45 degrees between the discharge port and the surface of the carbon / carbon composite material. The distance between the discharge port and the surface of the carbon / carbon composite material is 5 cm. Spray the surface of the material several times until the surface of the carbon / carbon composite material is completely and evenly covered with slurry.

[0084] (3) To improve the stability of the spraying process, the prepared material was slowly heated to 160°C at 5°C / min in an air atmosphere and kept warm for 5 min.

[0085] (4) In order to improve the bonding strength between the coating and the surface of the carbon / carbon composite material in practical applications, pyrolytic carbon was deposited using a chemical vapor deposition process at 1080°C with a methane to argon gas flow ratio of 1:4, and the time was controlled to 30 min as required.

[0086] The prepared high infrared emissivity coating has an average emissivity of 0.960 in the 1-22 μm band; after depositing the pyrolytic carbon layer, the average emissivity in the 1-22 μm band is 0.917, the floating values are all within 0.01, and the scratch destructive force of the coating is 28.5N; the coating described in this embodiment does not crack after 60 thermal cycles at 300°C↔-196°C.

[0087] Comparative Example 1

[0088] A coating (pure carbon black) with high infrared emissivity on the surface of a carbon / carbon composite material is prepared by the following method:

[0089] (1) Add 5 parts by mass of phenolic resin to 25 parts by mass of isopropanol solution and thoroughly sonicate until completely dissolved, and then set aside to obtain a phenolic resin isopropanol solution; add 5000 parts by mass of isopropanol, and then add nano carbon black in portions of 5 parts by mass each time, and add the next addition after each sonication for 5 minutes, adding a total of 20 parts by mass. When the obtained slurry is shaken, there should be no obvious agglomerated particles on the inner wall of the beaker, and a dispersed slurry is obtained; add the prepared phenolic resin isopropanol solution to the dispersed slurry, and then sonicate for 5 minutes to finally obtain a coating slurry.

[0090] (2) Use compressed air spraying technology and spray the carbon / carbon composite material surface with a spray gun. When spraying, pay attention to the angle of 45 degrees between the discharge port and the surface of the carbon / carbon composite material. The distance between the discharge port and the surface of the carbon / carbon composite material is 5-9 cm. Spray the surface of the material several times until the surface of the carbon / carbon composite material is completely and evenly covered with slurry.

[0091] (3) To improve the stability of the spraying process, the prepared material was slowly heated to 160°C at 5°C / min in an air atmosphere and kept warm for 5 min.

[0092] (4) In order to improve the bonding strength between the coating and the surface of the carbon / carbon composite material in practical applications, pyrolytic carbon was deposited using a chemical vapor deposition process at 1060°C with a methane to argon gas flow ratio of 1:4, and the time was controlled to be 15 min as required.

[0093] The prepared high infrared emissivity coating has an average emissivity of 0.957 in the 1-22 μm band; after the pyrolytic carbon layer is deposited, the average emissivity in the 1-22 μm band is 0.912, the floating values are all within 0.01, and the scratch destructive force of the coating is 19.5N; the coating in this comparative example has no cracking after 60 thermal cycles at 300°C↔-196°C, but when the coating is composed of only carbon black particles, the spherical carbon black particles are closely packed, and the pores between the particles are very small, which is not conducive to the subsequent deposition of pyrolytic carbon and easily causes pore sealing, such as Figure 5 As shown, the surface emissivity is greatly reduced.

[0094] Comparative Example 2

[0095] A coating with high infrared emissivity and strong bonding ability on the surface of a carbon / carbon composite material (without adding urea) is prepared by the following method:

[0096] (1) Add 5 parts by mass of phenolic resin to 25 parts by mass of isopropanol and thoroughly sonicate until completely dissolved, and then set aside to obtain a phenolic resin isopropanol solution; add 8 parts by mass of carbon nanotube dispersant to 25 parts by mass of carbon nanotubes, add 5500 parts by mass of isopropanol to dilute, and then sonicate for 20 minutes to evenly disperse; then add nano carbon black in portions of 5 parts by mass each time, and add the next addition after 5 minutes of sonication each time, adding a total of 15 parts by mass. When the obtained slurry is shaken, there should be no obvious agglomerated particles on the inner wall of the beaker, and a dispersed slurry is obtained; add 25 parts by mass of phenolic resin isopropanol solution to the dispersed slurry, and then sonicate for 5 minutes to obtain the final coating slurry.

[0097] (2) Use compressed air spraying technology and spray the carbon / carbon composite material surface with a spray gun. When spraying, pay attention to the angle of 60 degrees between the discharge port and the surface of the carbon / carbon composite material. The distance between the discharge port and the surface of the carbon / carbon composite material is 5-9 cm. Spray the surface of the material several times until the surface of the carbon / carbon composite material is completely and evenly covered with slurry.

[0098] (3) To improve the stability of the spraying process, the prepared material was slowly heated to 160°C at 5°C / min in an air atmosphere and kept warm for 5 min.

[0099] (4) In order to improve the bonding strength between the coating and the surface of the carbon / carbon composite material in practical applications, pyrolytic carbon was deposited using a chemical vapor deposition process at 1080°C with a methane to argon gas flow ratio of 1:5 for 15 min.

[0100] The prepared high infrared emissivity coating has an average emissivity of 0.960 in the 1-22 μm band; after the pyrolytic carbon layer is deposited, the average emissivity in the 1-22 μm band is 0.921, the floating values are all within 0.03, and the scratch destructive force of the coating is 22.3 N. The coating in this comparative example has no cracking after 60 thermal cycles at 300°C↔-196°C.

[0101] In order to illustrate the relevant properties of the coating provided by the present invention, the coating provided by the embodiment is analyzed and explained in combination with the comparative example. Figures 1 - 6 shown.

[0102] Figure 1 This is a scanning electron microscope photo of Example 1 after the spray coating step. Figure 2 This is a scanning electron microscope photograph of the coating after the heat treatment step in Example 1.Figure 2 Compared with Figure 1 it can be seen that the foaming phenomenon of urea produces a rich pore structure on the coating surface.

[0103] Figure 3 is the SEM image after the 15-min pyrolytic carbon deposition step in Example 1. After the 15-min pyrolytic carbon deposition, a large number of pore network structures can still be seen. Compared with Figure 5 the pore sealing phenomenon has been greatly improved.

[0104] Figure 4 is the mechanical properties of the scratch test of the coating before and after pyrolytic carbon deposition in Example 1. From Figure 4 it can be seen that the curve indicated by 0 min is the bonding strength of the coating without pyrolytic carbon deposition, and the curve indicated by 15 min is the bonding strength of the coating after 15-min pyrolytic carbon deposition. The abscissa is the bonding strength. It can be seen that at 0 min, the straight line shows a serrated change at about 10 N, indicating that the coating begins to be damaged. For the sample at 15 min, the straight line shows a serrated change at about 24 N, and the coating begins to be damaged. The bonding strength of the coating is about 24 N. From the changes of the upper and lower two lines, it can be seen that after pyrolytic carbon deposition, the bonding strength of the coating is improved.

[0105] Figure 5 is the microscopic morphology of the carbon black coating after pyrolytic carbon deposition in Comparative Example 1. From Figure 3 and Figure 5 it can be seen that the pore sealing phenomenon of the coating provided by the present invention has been greatly improved. Figure 5 The coating shown in is prepared from pure carbon black particles. The spherical carbon black particles are closely packed, and the pores between the particles are very small, which is not conducive to the subsequent deposition of pyrolytic carbon and is prone to pore sealing. That is to say, a little pyrolytic carbon deposition will block the pores; Figure 3 The coating in is composed of carbon black and carbon nanotubes. The carbon nanotubes with a large aspect ratio overlap with each other to form a large-pore network structure; subsequently, during the heat treatment process, a large amount of gas generated by the decomposition of urea further changes the position of the nanoparticles in the coating, further increasing the diameter of the pores, which is conducive to the deposition of pyrolytic carbon. It can be seen from the figure that after pyrolytic carbon deposition, the coating surface still has a large pore structure, which is in sharp contrast to Figure 5

[0106] Figure 6 are the SEM images before (a) and after (b) pyrolytic carbon deposition without adding urea. From Figure 6 it can be seen that without adding the urea foaming agent, the pore size on the coating surface decreases, the number decreases, the coating surface is uneven, and has strong inhomogeneity; when pyrolytic carbon is deposited, the network pore structure also shows an uneven distribution.

[0107] The present invention describes the preferred embodiments and their effects. However, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0108] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A coating with high infrared emissivity and strong bonding force on the surface of a carbon / carbon composite material, characterized in that, The coating components and the mass parts of each component are as follows: 22 - 26 parts of carbon nanotubes, 6 - 8 parts of carbon nanotube dispersant, 15 - 20 parts of nano carbon black, 3 - 5 parts of phenolic resin, 8 - 11 parts of urea, and 5000 - 6100 parts of isopropanol; A pyrolytic carbon layer is further provided on the coating; The high infrared emissivity and strong bonding force coating on the carbon / carbon composite material surface is prepared according to the following steps: Disperse the phenolic resin into 20 - 25 mass parts of isopropanol to obtain a phenolic resin solution; Add the carbon nanotube dispersant to the carbon nanotubes, and then add the remaining isopropanol for dilution to obtain a carbon nanotube solution; uniformly disperse the nano carbon black in the carbon nanotube solution to obtain a mixed solution; Add the phenolic resin solution to the mixed solution, and add urea, then mix evenly to obtain a coating slurry; Coat the coating slurry on the surface of the carbon / carbon composite material, and after heat treatment, the high infrared emissivity and strong bonding force coating on the carbon / carbon composite material surface is obtained; During the heat treatment process, it includes: slowly heating to 150 - 160 °C at 4 - 5 °C / min in an air atmosphere and holding for 5 min; After heat treatment, it further includes: under the condition that the gas flow ratio of methane to argon is 1:4 - 5, carry out pyrolytic deposition to obtain a pyrolytic carbon layer deposited on the high infrared emissivity and strong bonding force coating on the carbon / carbon composite material surface; The pyrolytic deposition temperature is 1060 - 1080 °C, and the deposition time is 15 - 30 min.

2. The high-infrared-emissivity and strong-bonding coating on the surface of the carbon / carbon composite material according to claim 1, wherein The coating components and the mass parts of each component are as follows: 26 parts of carbon nanotubes, 8 parts of carbon nanotube dispersant, 16 parts of nano carbon black, 5 parts of phenolic resin, 8 parts of urea, and 6022 parts of isopropanol.

3. The high-infrared-emissivity and strong-binding-force coating on the surface of the carbon / carbon composite material according to claim 1, wherein, The carbon nanotube dispersant is a carbon nanotube alcohol dispersant TNADIS.

4. A method for preparing a coating with high infrared emissivity and strong bonding force on the surface of a carbon / carbon composite material as described in claim 1, characterized in that, It includes the following steps: Disperse the phenolic resin into 20 - 25 mass parts of isopropanol to obtain a phenolic resin solution; Add the carbon nanotube dispersant to the carbon nanotubes, and then add the remaining isopropanol for dilution to obtain a carbon nanotube solution; uniformly disperse the nano carbon black in the carbon nanotube solution to obtain a mixed solution; Add the phenolic resin solution to the mixed solution, and add urea, then mix evenly to obtain a coating slurry; Coat the coating slurry on the surface of the carbon / carbon composite material, and after heat treatment, the high infrared emissivity and strong bonding force coating on the carbon / carbon composite material surface is obtained; During the heat treatment process, it includes: slowly heating to 150 - 160 °C at 4 - 5 °C / min in an air atmosphere and holding for 5 min; After heat treatment, it further includes: under the condition that the gas flow ratio of methane to argon is 1:4 - 5, carry out pyrolytic deposition to obtain a pyrolytic carbon layer deposited on the high infrared emissivity and strong bonding force coating on the carbon / carbon composite material surface; The pyrolytic deposition temperature is 1060 - 1080 °C, and the deposition time is 15 - 30 min.

5. The preparation method of the coating with high infrared emissivity and strong bonding force on the surface of the carbon / carbon composite material according to claim 4, wherein, During the process of coating the coating slurry on the surface of the carbon / carbon composite material, it includes: The coating slurry is sprayed onto the surface of the carbon / carbon composite material with a spray gun. When spraying, the angle between the discharge port and the surface of the carbon / carbon composite material is 45 - 60 degrees, and the distance between the discharge port and the surface of the carbon / carbon composite material is 5 - 9 cm. Each part of the material surface is sprayed several times until the surface of the carbon / carbon composite material is completely and evenly covered with the slurry.

6. Application of the coating according to claim 1 in a carbon / carbon composite material.

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