CN113023726B - Method for preparing high-thermal-conductivity carbon material by low-temperature CVD (chemical vapor deposition) method - Google Patents
Method for preparing high-thermal-conductivity carbon material by low-temperature CVD (chemical vapor deposition) method Download PDFInfo
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- CN113023726B CN113023726B CN202110412311.9A CN202110412311A CN113023726B CN 113023726 B CN113023726 B CN 113023726B CN 202110412311 A CN202110412311 A CN 202110412311A CN 113023726 B CN113023726 B CN 113023726B
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Abstract
The invention relates to a method for preparing a high-thermal-conductivity carbon material by a low-temperature CVD method, which takes silicon dioxide fiber as a deposition substratePreparing pyrolytic carbon by CVD at low surface temperature (1000-1300 ℃), etching the silicon dioxide fiber by hydrofluoric acid, depositing the pyrolytic carbon as a preform for the second time, and finally graphitizing the pyrolytic carbon in a graphitizing furnace at high temperature. The invention reduces the preparation temperature of the traditional CVD pyrolytic graphite from more than 1800 ℃ to less than 1200 ℃, effectively reduces the deposition temperature, and the density of the prepared sample piece is 1.85g/cm 3 Is lower than the traditional pyrolytic graphite (2.15-2.20 g/cm) 3 ) The thermal conductivity is as high as 503W/(m.DEG C), and is also higher than 350-400W/(m.DEG C) of the traditional CVD pyrolytic graphite.
Description
Technical Field
The invention belongs to the technical field of carbon materials, and relates to a method for preparing a high-thermal-conductivity carbon material by a low-temperature CVD method.
Background
The rapid development of aerospace, microelectronics and communication technologies puts higher requirements on heat management materials, and the traditional metal heat conduction materials such as aluminum, copper, silver and the like are difficult to meet the increasing heat dissipation requirements of electronic devices in the microelectronic field due to the limitations of high density, easy oxidation, low specific heat conductivity (ratio of heat conductivity to volume density), high Coefficient of Thermal Expansion (CTE) and the like. Chemical Vapor Deposition (CVD) carbon material/pyrolytic graphite due to its low bulk density (2.15-2.20 g/cm) 3 ) The material has high thermal conductivity, is rapidly developed into a class of heat conduction materials with the most prospect, and is widely applied to high-tech fields such as energy, calculation, communication, electronics, laser, space science and the like.
However, according to the literature "carbon material. Beijing: publication in metallurgical industry, 2004: 318-325', the deposition temperature of CVD pyrolytic graphite is usually above 1800 deg.C, the thermal conductivity is about 350-400W/(m.DEG C), the process has the defects of high deposition temperature, large equipment investment, high preparation cost and the like, and the heat rate also has a space for improvement.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a method for preparing a high-thermal-conductivity carbon material by a low-temperature CVD method.
Technical scheme
A method for preparing a high-thermal-conductivity carbon material by a low-temperature CVD method is characterized by comprising the following steps:
step 1: ultrasonically cleaning the silicon dioxide fiber bundle by using absolute ethyl alcohol, removing impurities and drying;
step 2: placing the silicon dioxide fiber bundle in a graphite mold by adopting an isothermal chemical vapor deposition process, and putting the silicon dioxide fiber bundle in an isothermal chemical vapor deposition furnace; vacuumizing a deposition furnace, heating the deposition furnace from room temperature to 1000-1300 ℃ under the protection of inert gas, introducing absolute ethyl alcohol serving as a carbon-hydrogen gas source precursor, controlling the pressure in the furnace to be 0.5-20.0 KPa, controlling the flow of the inert gas to be 50-300 mL/min, closing an absolute ethyl alcohol precursor gas valve and a power switch after the deposition is finished, gradually cooling the deposition furnace to room temperature under the protection of the inert gas, and taking a deposited silicon dioxide fiber bundle;
and 3, step 3: polishing the deposited silicon dioxide fiber bundle, then placing the silicon dioxide fiber bundle in hydrofluoric acid aqueous solution for ultrasonic treatment, cleaning and drying;
and 4, step 4: repeating the step 2 to carry out second isothermal chemical vapor deposition, and obtaining a pyrolytic carbon block after the deposition is finished;
and 5: and (2) putting the pyrolytic carbon block in a graphitization furnace, heating to 2200-3100 ℃ at the heating rate of 2 ℃/min, preserving heat, then closing a power supply, naturally cooling, and introducing inert gas in the whole graphitization process to obtain the carbon material with high thermal conductivity.
The cleaning in the step 3 adopts ultrasonic cleaning.
Advantageous effects
The invention provides a method for preparing a high-thermal-conductivity carbon material by a low-temperature CVD method, which is characterized in that silicon dioxide fibers are used as a deposition substrate, pyrolytic carbon is prepared on the surface of the deposition substrate by low-temperature (1000-1300 ℃) CVD, then the silicon dioxide fibers are etched by hydrofluoric acid, the etched pyrolytic carbon is used as a preform for second pyrolytic carbon deposition, and finally high-temperature graphitization treatment is carried out on the pyrolytic carbon in a graphitization furnace, so that the carbon material with the thermal conductivity up to 503W/(m DEG C) is prepared.
Method of the invention. By introducing the silicon dioxide fibers as the deposition substrate, compared with a common planar substrate, the carbon layer deposition efficiency is greatly improved due to the ultrahigh specific surface area of silicon dioxide, and the problem of insufficient carbon layer deposition efficiency caused by low preparation temperature is effectively solved. In the example 2 of the invention, the preparation temperature of the traditional CVD pyrolytic graphite is reduced from more than 1800 ℃ to less than 1200 ℃, the deposition temperature is effectively reduced, and the density of the prepared sample piece is 1.85g/cm 3 Is lower than the traditional pyrolytic graphite (2.15-2.20 g/cm) 3 ) The thermal conductivity is as high as 503W/(m.DEG C.), and is higher than 350-400W/(m.DEG C.) of the traditional CVD pyrolytic graphite.
Drawings
FIG. 1 is a process flow diagram of a low temperature CVD method for preparing a high thermal conductivity carbon material.
FIG. 2 is an apparatus diagram of an isothermal chemical vapor deposition furnace.
As shown in the figures, the list of reference numbers is as follows:
1: gas supply (absolute ethanol + inert gas), 2: graphite jig, 3: thermocouple, 4: deposition substrate, 5: graphite air duct, 6: heating body
FIG. 3 is a diagram of a carbon material PLM prepared in example 2.
FIG. 4 is an SEM image of the carbon material prepared in example 2.
Detailed Description
The invention will now be further described with reference to the following examples and drawings:
example 1:
the method comprises the following steps: cutting silica fiber with the diameter of 5 mu m into chopped fiber with the length of 21mm, and unidirectionally paving the chopped fiber in a graphite mold with the size of 80mm multiplied by 20mm, wherein the volume fraction of the silica fiber is designed to be 30%;
step two: placing a mold filled with silicon dioxide fibers in a vapor deposition furnace by adopting an isothermal chemical vapor deposition process, vacuumizing, heating to 1100 ℃ at a heating rate of 10 ℃/min under the protection of nitrogen, introducing absolute ethyl alcohol and nitrogen after the temperature is reached, controlling the flow rate of the nitrogen at 200mL/min, controlling the flow rate of the absolute ethyl alcohol at 11g/h, controlling the pressure in the furnace at 2.0KPa, closing an absolute ethyl alcohol valve after deposition for 48h, naturally cooling under the protection of the nitrogen, and taking out a sample;
step three: polishing the sample obtained in the second step by using 800-mesh abrasive paper, cutting the sample into pieces with the thickness of 4mm by using a cutting machine, putting the pieces into a 100mL plastic beaker, pouring 40% of hydrofluoric acid by mass fraction, immersing the sample, sealing the sample by using a preservative film, performing ultrasonic treatment at 60 ℃ for 96 hours to obtain a pyrolytic carbon preform, taking out the sample, putting the sample into deionized water, performing ultrasonic cleaning for 12 hours, and drying for later use;
step four: putting the sample piece obtained in the third step into an isothermal deposition furnace for second pyrolytic carbon deposition, wherein the specific operation flow is shown in the second step, and the deposition time is prolonged to 120h to obtain a pyrolytic carbon block;
step five: putting the pyrolytic carbon block in an isothermal furnace, heating from room temperature to 2200 ℃ at the heating rate of 2 ℃/min, preserving heat for 2h, then cooling from 2200 ℃ to 1000 ℃ at the cooling rate of 80 ℃/min, turning off a power supply, and naturally cooling. Argon is always introduced in the whole graphitization process, and the flow rate of the argon is controlled at 50mL/min.
Example 2:
the method comprises the following steps: cutting silica fiber with diameter of 8 μm into chopped fiber with length of 21mm, and unidirectionally spreading in graphite mold with size of 80mm × 80mm × 20mm to design silica fiber volume fraction of 40%;
step two: placing a mold filled with silicon dioxide fibers in a vapor deposition furnace by adopting an isothermal chemical vapor deposition process, vacuumizing, heating up to 1160 ℃ at a heating rate of 10 ℃/min under the protection of nitrogen, introducing absolute ethyl alcohol and nitrogen after the temperature is reached, controlling the flow rate of the nitrogen at 200mL/min, controlling the flow rate of the absolute ethyl alcohol at 11g/h, controlling the pressure in the furnace at 3.5KPa, closing an absolute ethyl alcohol valve after 60h of deposition, naturally cooling under the protection of the nitrogen, and taking out a sample;
step three: polishing the sample obtained in the second step by using 800-mesh abrasive paper, cutting the sample into pieces with the thickness of 4mm by using a cutting machine, putting the pieces into a 100mL plastic beaker, pouring 40% of hydrofluoric acid by mass fraction, immersing the sample, sealing the sample by using a preservative film, performing ultrasonic treatment at 60 ℃ for 96 hours to obtain a pyrolytic carbon preform, taking out the sample, putting the sample into deionized water, performing ultrasonic cleaning for 12 hours, and drying for later use;
step four: putting the sample piece obtained in the third step into an isothermal deposition furnace for second pyrolytic carbon deposition, wherein the specific operation flow is shown in the second step, and the deposition time is prolonged to 420h to obtain a pyrolytic carbon block;
step five: putting the pyrolytic carbon block in an isothermal furnace, heating from room temperature to 2450 ℃ at the heating rate of 2 ℃/min, preserving heat for 2 hours, then cooling from 2450 ℃ to 1000 ℃ at the cooling rate of 80 ℃/min, turning off a power supply, and naturally cooling. Argon is always introduced in the whole graphitization process, and the flow rate of the argon is controlled at 50mL/min.
Example 3:
the method comprises the following steps: cutting silica fiber with diameter of 15 μm into chopped fiber with length of 21mm, and unidirectionally spreading in graphite mold with size of 80mm × 80mm × 20mm to design silica fiber volume fraction of 50%;
step two: placing a mold filled with silicon dioxide fibers in a vapor deposition furnace by adopting an isothermal chemical vapor deposition process, vacuumizing, heating to 1180 ℃ at a heating speed of 10 ℃/min under the protection of nitrogen, introducing absolute ethyl alcohol and nitrogen after the temperature is reached, controlling the flow rate of inert gas to be 200mL/min, controlling the flow rate of the absolute ethyl alcohol to be 11g/h, controlling the pressure in the furnace to be 4.0KPa, closing an absolute ethyl alcohol valve after deposition is carried out for 72h, naturally cooling under the protection of nitrogen, and taking out a sample piece;
step three: polishing the sample obtained in the second step by using 800-mesh abrasive paper, cutting the sample into 4mm thick pieces by using a cutting machine, putting the sample into a 100mL plastic beaker, pouring 40% mass fraction of hydrofluoric acid, immersing the sample, sealing the sample by using a preservative film, performing ultrasonic treatment for 96 hours at 60 ℃ to obtain a pyrolytic carbon preform, taking out the sample, putting the sample into deionized water, performing ultrasonic cleaning for 12 hours, and drying for later use;
step four: putting the sample piece obtained in the third step into an isothermal deposition furnace for second pyrolytic carbon deposition, wherein the specific operation flow is shown in the second step, and the deposition time is prolonged to 480h to obtain a pyrolytic carbon block;
step five: putting the pyrolytic carbon block in an isothermal furnace, heating from room temperature to 3100 ℃ at a heating rate of 2 ℃/min, preserving heat for 2h, then cooling from 3100 ℃ to 1000 ℃ at a cooling rate of 80 ℃/min, turning off a power supply, and naturally cooling. Argon is always introduced in the whole graphitization process, and the flow rate of the argon is controlled at 50mL/min.
Claims (2)
1. A method for preparing a high-thermal-conductivity carbon material by a low-temperature CVD method is characterized by comprising the following steps:
step 1: ultrasonically cleaning the silicon dioxide fiber bundle by using absolute ethyl alcohol, removing impurities and drying;
step 2: placing the silicon dioxide fiber bundle in a graphite mold by adopting an isothermal chemical vapor deposition process, and putting the silicon dioxide fiber bundle in an isothermal chemical vapor deposition furnace; vacuumizing a deposition furnace, raising the temperature from room temperature to 1000-1300 ℃ under the protection of inert gas, introducing absolute ethyl alcohol serving as a carbon-hydrogen gas source precursor, controlling the pressure in the furnace to be 0.5-20.0 KPa, controlling the flow of the inert gas to be 50-300 mL/min, closing an absolute ethyl alcohol precursor gas valve and a power switch after deposition is finished, gradually lowering the temperature to the room temperature under the protection of the inert gas, and taking a deposited silicon dioxide fiber bundle;
and 3, step 3: polishing the deposited silicon dioxide fiber bundle, then placing the silicon dioxide fiber bundle in hydrofluoric acid aqueous solution for ultrasonic treatment, cleaning and drying;
and 4, step 4: repeating the step 2 to carry out second isothermal chemical vapor deposition, and obtaining a pyrolytic carbon block after the deposition is finished;
and 5: and (2) putting the pyrolytic carbon block in a graphitization furnace, heating to 2200-3100 ℃ at the heating rate of 2 ℃/min, preserving heat, then closing a power supply, naturally cooling, and introducing inert gas in the whole graphitization process to obtain the carbon material with high thermal conductivity.
2. The method for producing a high thermal conductivity carbon material by a low temperature CVD method according to claim 1, wherein: and 3, ultrasonic cleaning is adopted for cleaning in the step 3.
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| CN111847440A (en) * | 2019-04-30 | 2020-10-30 | 中国科学院宁波材料技术与工程研究所 | Preparation method and application of graphitized carbon nano-belt and composite material thereof |
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