A method for preparing a helical carbon fiber framework system

Abstract

The present invention discloses a preparation system for a helical carbon fiber skeleton, which relates to the field of material preparation. The preparation system for the helical carbon fiber skeleton includes: a circuit module for providing a controllable electric arc for a growth module; a gas circuit module for providing a mixed gas of hydrogen and anhydrous ethanol gas for the growth module. The beneficial effects of the present invention are as follows: The present invention creates helical carbon fibers by means of arc discharge under atmospheric pressure, can switch the growth conditions within a few seconds, and can control the helical carbon fibers to be in different growth environments at different time periods; enables the helical carbon fibers to have the ability to re-nucleate and grow on the surface, simplifying the growth difficulty of the helical carbon fibers; regulates the helical diameter through the electrode temperature, and the helices hook each other to form a uniform skeleton; this skeleton has large deformation and good synergistic ability, uniform spatial distribution, and the helical carbon fibers hook each other, showing isotropic mechanical properties; and can be applied to the preparation of isotropic carbon fiber reinforced composites.

Description

Technical Field

[0001] The present invention relates to the field of material preparation, and specifically to a method for preparing a helical carbon fiber skeleton system. Background Art

[0002] Carbon fiber has excellent mechanical properties, and the tensile strength of the grown carbon fiber is usually about 100 GPa. The tensile strength of about 4 GPa can also be obtained by high-temperature carbonization and graphitization of organic fibers.

[0003] Helical carbon fiber can increase the strain capacity of the fiber. The existing helical carbon fiber uses chemical vapor deposition (CVD). After adding a catalyst, the helical carbon fiber will grow helically on the surface of the catalyst. The total number of helical carbon fibers obtained is limited by the number of the initial catalyst. The result is that the spacing between adjacent helical fibers is greater than the diameter of the helical fiber, and the helical carbon fibers do not hook each other. And because the growth direction of the carbon fiber is induced by the direction of the catalyst, the sample as a whole will show anisotropy. From a macroscopic perspective, the mechanical properties in the helical growth direction are significantly different from those in the helical sidewall direction.

[0004] The currently used chemical vapor deposition equipment uses an electric furnace, which has a delay effect on the control of the growth temperature required for helical carbon fiber. It takes more than ten minutes to complete the switching of different growth temperatures and cannot quickly reach the temperature required for carbon fiber of the expected size, so it needs to be improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a helical carbon fiber skeleton system to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A method for preparing a helical carbon fiber skeleton system, comprising:

[0008] A circuit module for providing a controllable electric arc for the growth module;

[0009] A gas circuit module for providing a mixed gas of hydrogen and anhydrous ethanol for the growth module;

[0010] A growth module for generating a helical carbon fiber skeleton;

[0011] The circuit module is connected to the growth module, and the gas circuit module is connected to the growth module.

[0012] As a further solution of the present invention: The circuit module includes an adjustable DC power supply, a current-limiting resistor, an inductor, a capacitor, a first tungsten needle electrode, and a second tungsten needle electrode. The positive pole of the adjustable DC power supply is connected to one end of the current-limiting resistor, and the negative pole of the adjustable DC power supply is connected to one end of the first tungsten needle electrode and one end of the capacitor. The other end of the current-limiting resistor is connected to one end of the inductor and the other end of the capacitor, and the other end of the inductor is connected to the second tungsten needle electrode.

[0013] As a further solution of the present invention: The electrode spacing between the first tungsten needle electrode and the second tungsten needle electrode is adjusted by a stepper motor.

[0014] As a further solution of the present invention: The gas path module includes a hydrogen generator, an alcohol bottle filled with anhydrous ethanol, a water bath heating device, a first glass tube, and a second glass tube. The hydrogen output by the hydrogen generator is inserted into the anhydrous ethanol below through the first glass tube, and the upper part of the anhydrous ethanol in the alcohol bottle is connected to the growth module through the second glass tube. A water bath heating device is provided below the alcohol bottle.

[0015] As a further solution of the present invention: The growth module includes a graphite block and a growth point. The graphite block has cross-shaped holes. The first end of the cross-shaped holes is connected to the gas path module, the second end and the third end of the cross-shaped holes are connected to the circuit module, an electric arc is generated by the circuit module in the middle of the cross-shaped holes, the fourth end of the cross-shaped holes is provided with a growth point, and a substrate is placed at the growth point to grow spiral carbon fibers.

[0016] As a further solution of the present invention: There is a ceramic tube between the second end and the third end of the cross-shaped holes and the connection to the circuit module.

[0017] As a further solution of the present invention: There will be a gap between the connection to the circuit module and the ceramic tube.

[0018] As a further solution of the present invention: The pipe diameter of the first end of the cross-shaped holes should be less than or equal to the electrode spacing between the two tungsten needle electrodes connected to the circuit module at the second end and the third end of the cross-shaped holes.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention creates spiral carbon fibers by applying arc discharge under atmospheric pressure, can switch growth conditions within a few seconds, and can control the spiral carbon fibers to be in different growth environments at different time periods; enables the spiral carbon fibers to have the ability to re-nucleate and grow on the surface, simplifying the growth difficulty of the spiral carbon fibers; regulates the spiral diameter through the electrode temperature, and the spirals hook each other to form a uniform skeleton; this skeleton has a large deformation and good synergy ability, uniform spatial distribution, and the spiral carbon fibers hook each other, showing isotropic mechanical properties; can be applied to the preparation of isotropic carbon fiber reinforced composites. Description of the Drawings

[0020] Figure 1It is a schematic diagram for preparing a helical carbon fiber skeleton system.

[0021] Figure 2 It is the first part of the circuit diagram for preparing a helical carbon fiber skeleton system.

[0022] Figure 3 It is the second part of the circuit diagram for preparing a helical carbon fiber skeleton system.

[0023] In the figure: 1 - circuit module, 2 - gas circuit module, 3 - growth module, 11 - adjustable DC power supply, 12 - current limiting resistor, 13 - inductor, 14 - capacitor, 15 - first tungsten needle electrode, 16 - second tungsten needle electrode, 21 - hydrogen generator, 22 - alcohol bottle, 23 - water bath heating device, 24 - first glass tube, 25 - second glass tube, 31 - graphite block, 32 - growth point. Specific embodiments

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] Please refer to Figure 1 , a system for preparing a helical carbon fiber skeleton, including:

[0026] The circuit module 1 is used to provide a controllable electric arc for the growth module 3;

[0027] The gas circuit module 2 is used to provide a mixed gas of hydrogen and anhydrous ethanol gas for the growth module 3;

[0028] The growth module 3 is used to generate a helical carbon fiber skeleton;

[0029] The circuit module 1 is connected to the growth module 3, and the gas circuit module 2 is connected to the growth module 3.

[0030] In this embodiment: Please refer to Figure 1 , the circuit module 1 includes an adjustable DC power supply 11, a current limiting resistor 12, an inductor 13, a capacitor 14, a first tungsten needle electrode 15, and a second tungsten needle electrode 16. The positive pole of the adjustable DC power supply 11 is connected to one end of the current limiting resistor 12, the negative pole of the adjustable DC power supply 11 is connected to one end of the first tungsten needle electrode 15 and the capacitor 14, the other end of the current limiting resistor 12 is connected to one end of the inductor 13 and the other end of the capacitor 14, and the other end of the inductor 13 is connected to the second tungsten needle electrode 16.

[0031] There is a partial gap between the two tungsten needle electrodes for arc discharge. The current-limiting resistor 12 and the capacitor 14 jointly control the arc discharge frequency. The capacitor 14 is used to limit the energy of a single arc discharge. The inductor 13 is used to increase the voltage between the two electrodes when the arc is interrupted. The DC power supply is responsible for applying a high voltage between the two electrodes. The regulation of the arc includes controlling the power supply voltage, the capacitance of capacitor 14, the resistance, and the inductance of inductor 13, as well as the distance between the two tungsten needle electrodes. Multiple control conditions are superimposed to jointly adjust the arc discharge power. The electrode temperature is adjusted by the arc power. The power P = UI - RI², where U is the power supply voltage, R is the current-limiting resistor 12, and I is the current in the circuit. The current I is adjusted by using the electrode gap. The larger the gap, the smaller the current.

[0032] In this embodiment: Please refer to Figure 1 , the electrode distance between the first tungsten needle electrode 15 and the second tungsten needle electrode 16 is adjusted by a stepper motor.

[0033] Since the electrode distance used is adjusted by a stepper motor, the power regulation of the arc during the growth process is fast and precise. The growth temperature control of the spiral carbon fiber reacts quickly, and the reaction time is much less than the adjustment time of the chemical vapor deposition method equipment. Using a stepper motor with a pitch of 1 mm and a step angle of 1.8° for regulation, a fine adjustment of 5 μm can be performed. The electrode distance set by program control can be in place within 1 s, and the electrode will reach a new equilibrium temperature within a few seconds. Therefore, this technology can quickly switch the growth conditions and provide more ways to optimize the properties of composite materials.

[0034] In this embodiment: Please refer to Figure 2 , the gas path module 2 includes a hydrogen generator 21, an alcohol bottle 22 filled with absolute ethanol, a water bath heating device 23, a first glass tube 24, and a second glass tube 25. The hydrogen output by the hydrogen generator 21 passes through the first glass tube 24 and is inserted below the absolute ethanol in the alcohol bottle 22. The upper part of the absolute ethanol in the alcohol bottle 22 is connected to the growth module 3 through the second glass tube 25. A water bath heating device 23 is provided below the alcohol bottle 22.

[0035] After the hydrogen is released by the hydrogen generator 21, the hydrogen is connected to the first glass tube 24 through a rubber hose. The hydrogen immerses below the liquid level of the absolute ethanol. Under the action of air pressure, the hydrogen floats up and enters the gas part above the liquid level of the alcohol bottle 22. After being fully mixed with the vaporized absolute ethanol, it is introduced into the growth module 3.

[0036] By using the water bath heating device 23 to control the temperature of absolute ethanol in the alcohol bottle 22, the vapor pressure of absolute ethanol is adjusted, so that the carbon concentration in the gas flow finally flowing into the arc discharge area can be quantitatively adjusted. Different combinations of carbon concentration and nucleation number will produce carbon fibers of different sizes. Less nucleation and high carbon concentration will grow into thicker fibers; more nucleation and low carbon concentration will grow into thinner fibers; more nucleation and high carbon concentration will grow small burrs on the thicker fibers.

[0037] In this embodiment: Please refer to Figure 3 , the growth module 3 includes a graphite block 31 and a growth point 32. The graphite block 31 has cross-shaped holes. The first end of the cross-shaped holes is connected to the gas path module 2, and the second and third ends of the cross-shaped holes are connected to the circuit module 1. The circuit module 1 generates an arc in the middle of the cross-shaped holes. The fourth end of the cross-shaped holes is provided with a growth point 32, and a substrate is placed at the growth point 32 to grow helical carbon fibers.

[0038] The substrate is usually selected from products with catalytic effects such as iron-nickel, and iron wires and iron nets are commonly used.

[0039] The formation process of helical carbon fibers is as follows. When there are SP3 substituted SP2 hybrid carbon atoms in the carbon fiber, the SP3 bonds are not coplanar, which will cause the carbon layer to bend. Simply put, the more SP3 hybrid carbon atoms in the carbon fiber, the more severely the carbon fiber bends, and the smaller the helical diameter.

[0040] The formation process of the skeleton is as follows. The carbon fibers in this technology all grow in a bent shape and have the ability to nucleate again on the fiber surface and grow into carbon fibers. This enables the original substrate carbon fibers and the newly grown carbon fibers on them to grow together and extend in circles along a certain helical trajectory. Especially when multiple nearby carbon fibers grow together, these helical carbon fibers will be entangled and hooked together to form a uniform isotropic skeleton.

[0041] In this embodiment: Please refer to Figure 3 , there is a ceramic tube between the second and third ends of the cross-shaped holes and the circuit module 1 connected.

[0042] The outer diameter of the ceramic tube should ensure that the distance between the electrode and the cavity is greater than the distance between the two electrodes during operation. Otherwise, sidewall discharge is likely to occur and burn the cavity.

[0043] In this embodiment: Please refer to Figure 3 , there will be a gap between the circuit module 1 connected and the ceramic tube.

[0044] A minute gap allows a small amount of air to enter the cavity. When it diffuses near the electrode discharge area, it will oxidize the electrode to generate tungsten oxide. The boiling point of tungsten oxide is around 1700 degrees Celsius. The high temperature of the electrode will vaporize the tungsten oxide and re-condense it into small particles in the low-temperature part of the cavity. Tungsten oxide can also be reduced to tungsten by hydrogen and carbon, and it can catalyze the formation of carbon fibers. Simply put, the gap can regulate the number of primary nuclei.

[0045] In this embodiment: Please refer to Figure 3 , the pore diameter of the first-end pipe of the cross-shaped hole should be less than or equal to the distance between the two tungsten needle electrodes connected to the circuit module 1 at the second and third ends of the cross-shaped hole.

[0046] The pore diameter of the gas inlet pipe should be comparable to the distance between the two tungsten needle electrodes to ensure that the introduced gas all passes through the arc area;

[0047] SP3 carbon atoms are more likely to form and be maintained in the presence of atomic hydrogen. The relationship between the concentration of atomic hydrogen and temperature is an exponential change. Approximately, for every 300-degree increase in temperature, the concentration of atomic hydrogen doubles. In this technology, the content of SP3 carbon atoms is regulated through two points, and then the size of the helical diameter is regulated. One is the electrode temperature. The higher the electrode temperature, the higher the concentration of atomic hydrogen in the gas flow passing through the discharge area. The other is the ratio of the diameter of the air inlet hole to the electrode diameter. At the same electrode temperature, the larger the ratio of the diameter of the air inlet hole to the electrode diameter, the smaller the content of atomic hydrogen in the whole atmosphere. Correspondingly, carbon fibers with a larger helical diameter will be formed.

[0048] Specific application example: The substrate used in the experiment is an iron substrate, which plays an important catalytic role in the growth of helical carbon fibers throughout the growth process and provides a strong attachment point for the helical carbon fiber products. It is an important condition for the formation of helical carbon fibers.

[0049] This technology uses high-temperature pyrolysis of carbon-containing gas sources near 3400 degrees Celsius, so it is applicable to all carbon-containing gases or vapors with a pyrolysis temperature lower than 3400 degrees Celsius.

[0050] 1. Controllable adjustment of the size of helical carbon fibers

[0051] The electrode diameter is 1.6 mm, the inner diameter of the porcelain tube is 2 mm, and the diameter of the air inlet pipe is 2 mm. By controlling the power supply voltage at 555 V, the resistance at 155 Ω, the capacitance at 1 μF, the inductance at 200 μH, and the water bath temperature at 25 °C, the current is controlled at 2.6 A. At this time, the arc power is about 394 W. First, let the growth equipment preheat for 5 minutes. After the surface of the graphite block shows a red-hot phenomenon, put in the iron wire substrate. Set the growth time to 30 minutes, and a sample of helical carbon fibers can be obtained. Under a high-definition camera, the diameter of the helical carbon fiber sample is about 1 μm, and the helical radius is about 25 μm.

[0052] Large-size helical carbon fibers

[0053] Control the distance between two tungsten needle electrodes to make the current reach 2.2 A. At this time, the arc discharge power is approximately 470 W. According to the same growth time, spiral carbon fibers of different sizes will be obtained. At this time, the spiral radius of the spiral carbon fiber under the high-definition camera is about 3 μm.

[0054] Small-sized spiral carbon fiber

[0055] By controlling the distance between the tungsten needle electrodes, the arc power can be smoothly changed, and spiral carbon fibers with gradually changing sizes can be obtained therefrom.

[0056] Spiral carbon fibers of different sizes can be obtained using different powers. The agglomeration abilities of spiral carbon fibers of different sizes are different. The macroscopic manifestation of this agglomeration ability is the different hardness of the skeletons. Some large-sized spiral carbon fibers can agglomerate into hard lumps, and these hard lumps can cut through paper; while small-sized spiral carbon fibers only agglomerate into soft lumps, and these soft lumps cannot cut through paper but turn into powder themselves.

[0057] 2. Example of secondary growth on the surface of spiral carbon fiber, the appearance of burr phenomenon and the final formation of carbon skeleton Set the water bath temperature to 40 °C, the carbon concentration in the gas flow can be changed, and small fibers can grow on the surface of the spiral carbon fiber. This phenomenon indicates that the smooth surface of the spiral carbon fiber has the ability of secondary growth. This ability to grow again on the surface of the carbon fiber is the basis for preparing the spiral carbon fiber skeleton. After the appearance of small burrs, with the passage of time, the length and size of the burrs will gradually increase, and finally evolve into multiple carbon fibers growing along other directions on the surface of a main carbon fiber.

[0058] The appearance of burrs on the fiber

[0059] As the growth time increases, carbon fibers will also appear to grow again by secondary nucleation on the surface of the carbon fibers growing along other directions. The process of growing fibers on fibers is repeated continuously, and finally there will be mutual hook and entanglement between the spiral carbon fibers, and finally a carbon skeleton is formed. Since the growth directions of the internal spiral carbon fibers of this skeleton have the same probability in all directions, it has isotropic mechanical properties as a whole.

[0060] 3. Ultra-large carbon fiber

[0061] When the growth conditions are set as the power supply voltage of 555 V, the resistance of 155 Ω, the capacitance of 1 μF, the inductance of 200 μH, and the water bath temperature of 25 °C, an ultra-large carbon fiber with a fiber radius of 22 μm can be grown while growing spiral carbon fibers.

[0062] Under the same growth conditions, super-large carbon fibers will grow simultaneously with helical carbon fibers, but the number of super-large carbon fibers will be much smaller than that of helical carbon fibers. These super-large carbon fibers will serve as secondary substrates for the growth of helical carbon fibers, and the helical carbon fibers will attach and grow on their surfaces, gradually growing a carbon fiber skeleton.

[0063] In addition, the growth conditions of super-large carbon fibers are similar to those of helical carbon fibers, and different helical carbon fibers and corresponding super-large carbon fibers will grow under different growth conditions.

[0064] The working principle of the present invention is as follows: The circuit module 1 is used to provide a controllable electric arc for the growth module 3; the gas circuit module 2 is used to provide a mixed gas of hydrogen and anhydrous ethanol gas for the growth module 3; the growth module 3 is used to generate a helical carbon fiber skeleton. The present invention prepares helical carbon fibers by arc discharge under atmospheric pressure, can switch the growth conditions within a few seconds, and can control the helical carbon fibers to be in different growth environments at different time periods; enables the helical carbon fibers to have the ability to re-nucleate and grow on the surface, simplifying the growth difficulty of the helical carbon fibers; regulates the helical diameter through the electrode temperature, and the helices hook each other to form a uniform skeleton; this skeleton has large deformation and good synergistic ability, uniform spatial distribution, and the helical carbon fibers hook each other, showing isotropic mechanical properties; it can be applied to the preparation of isotropic carbon fiber reinforced composites.

[0065] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed claims.

[0066] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A preparation method of a helical carbon fiber skeleton system, characterized in that: The preparation helical carbon fiber skeleton system includes: A circuit module for providing a controllable electric arc for the growth module; A gas circuit module for providing a mixed gas of hydrogen and gaseous absolute ethanol for the growth module; A growth module for generating a helical carbon fiber skeleton; The circuit module is connected to the growth module, and the gas circuit module is connected to the growth module; The circuit module includes an adjustable DC power supply, a current-limiting resistor, an inductor, a capacitor, a first tungsten needle electrode, and a second tungsten needle electrode. The positive pole of the adjustable DC power supply is connected to one end of the current-limiting resistor, and the negative pole of the adjustable DC power supply is connected to the first tungsten needle electrode and one end of the capacitor. The other end of the current-limiting resistor is connected to one end of the inductor and the other end of the capacitor, and the other end of the inductor is connected to the second tungsten needle electrode; The growth module includes a graphite block and a growth point. The graphite block has a cross-shaped hole. The first end of the cross-shaped hole is connected to the gas circuit module, and the second end and the third end of the cross-shaped hole are connected to the circuit module. The electric arc generated by the circuit module is in the middle of the cross-shaped hole. The fourth end of the cross-shaped hole is provided with a growth point, and a substrate is placed at the growth point to grow helical carbon fibers.

2. The preparation of the spiral carbon fiber skeleton system according to claim 1, characterized in that, The electrode spacing between the first tungsten needle electrode and the second tungsten needle electrode is adjusted by a stepping motor.

3. The preparation method of the spiral carbon fiber skeleton system according to claim 1, wherein, The gas circuit module includes a hydrogen generator, an alcohol bottle filled with absolute ethanol, a water bath heating device, a first glass tube, and a second glass tube. The hydrogen output by the hydrogen generator is inserted into the absolute ethanol below through the first glass tube. The upper part of the absolute ethanol in the alcohol bottle is connected to the growth module through the second glass tube, and a water bath heating device is provided below the alcohol bottle.

4. The method for preparing the helical carbon fiber framework system according to claim 1, wherein There is a ceramic tube between the second end and the third end of the cross-shaped hole and the circuit module connected thereto.

5. The preparation of the helical carbon fiber skeleton system according to claim 4, characterized in that, There will be a gap between the circuit module connected and the ceramic tube.

6. The method for preparing a helical carbon fiber framework system according to any one of claims 1, 4, and 5, wherein The pipe diameter of the first end of the cross-shaped hole should be less than or equal to the electrode spacing between the two tungsten needle electrodes connected to the second end and the third end of the cross-shaped hole of the circuit module.

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