A nanofiber and its preparation method

Abstract

The present invention provides a nanofiber and its preparation method. The preparation method uses carbon nanotubes as templates, reacts silicon source material on the carbon nanotubes to form a silicon carbide coating layer, and then oxidizes it to form a silicon oxide nanofiber. The diameter of the nanofiber prepared by the preparation method can be reduced to 20-100 nm, and the uniformity is high.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication technology, specifically relating to a nanofiber and its preparation method. Background Technology

[0002] The development of optical fiber communication technology has had a profound impact on the entire telecommunications network and information industry. Its evolution and development will largely determine the future landscape of these sectors. The development of optical communication hinges on the development of its components, which in turn requires a revolution in materials. Ordinary optical fibers have a bandwidth of 25 THz, offering enormous transmission capacity. However, the transmission rate of current optical fiber communication systems is far below this 25 THz capacity. To achieve high-speed optical communication, the "bottleneck effect" must be overcome. Existing materials cannot adequately meet these requirements, but research into the application of nanotechnology suggests the potential to break through traditional limitations, enabling a closer integration of microelectronics and optoelectronics, and significantly improving the performance of optoelectronic devices.

[0003] Since the discovery of carbon nanotubes in 1991, scientists have been hoping to create nanofiber materials composed of carbon nanotubes. Nanofiber arrays are predicted to have high toughness, strength and hardness, and have great potential in applications such as underwater optical cables, smart bulletproof vests and monochromatic light transmission. Due to the tight arrangement between carbon atoms, a single carbon nanotube has become one of the toughest materials in the world. However, how to weave a single carbon nanotube into an existing optical fiber material has become a huge problem for scientists. The existing optical fiber preparation technologies are mainly as follows: (1) Crystal semiconductor nanowires prepared by laser ablation method. The single crystal silicon and germanium optical waveguides synthesized by this method have diameters ranging from 6-20 nm and lengths ranging from 1-30 μm. However, their surface roughness and diameter uniformity are very poor, which leads to extremely high losses in this semiconductor nanowire. (2) Typical silicon material micron and nano-sized device preparation methods include lithography and etching. These processes are very expensive, and their decomposition process is limited, and the preparation process is slow. (3) One-step laser heating stretching method for photonic crystal fibers: Although the inner diameter of the small-diameter photonic crystal fibers prepared by this method reaches the nanometer scale, the overall size does not meet the nanometer scale requirement. (4) Two-step flame heating stretching method for silicon oxide fibers: This method requires the introduction of a tapered sapphire rod with a tip diameter of approximately 80 μm. The disadvantage of this method is that the size of the fiber stretched in the first step is difficult to determine, and the fiber is difficult to wind onto the sapphire rod in the second step. Therefore, it is difficult to implement the experiment. All of the above preparation methods can only be used to prepare single or multiple nanofibers under a microscope, and cannot obtain a uniform nanofiber array. Summary of the Invention

[0004] To address the problems existing in the fabrication of nanofibers in the prior art, the present invention provides a uniformly sized nanofiber and its fabrication method, the specific solution of which is as follows:

[0005] A method for preparing a nanofiber includes the following steps:

[0006] S1: Coating step, in which a silicon source material reacts with a carbon source material including carbon nanotubes to form a silicon carbide coating layer on the surface of the carbon nanotubes;

[0007] S2: Oxidation step, in which the carbon nanotubes after the coating step are oxidized to silicon carbide to silicon oxide;

[0008] S3: Cleaning step, cleaning the carbon nanotubes after the oxidation step to obtain the nanofiber.

[0009] Optionally, the carbon nanotubes after the coating step are carbon nanotube arrays.

[0010] Optionally, under the action of external force, the carbon nanotubes with silicon carbide coating are heated instantaneously by electric heating or high-voltage electric arc to form the carbon nanotube array.

[0011] Optionally, in step S1, a resin coating layer containing a silicon source material is formed on the surface of the carbon nanotubes by a silicon source material, carbon nanotubes, and resin, and then the silicon carbide coating layer is formed at a temperature of 1300-1500°C in an inert atmosphere or an inert atmosphere containing a carbon source gas.

[0012] Optionally, the resin is a thermosetting resin.

[0013] Optionally, the thermosetting resin is a phenolic resin.

[0014] Optionally, the silicon source material is 4 to 6 parts by weight, the carbon nanotubes are 2 to 3 parts by weight, and the resin is 50 to 60 parts by weight.

[0015] Optionally, the carbon source gas is acetylene.

[0016] Optionally, the silicon source material is silicon powder or diatomaceous earth.

[0017] Optionally, in step S2, the oxidation is carried out in an oxygen atmosphere by electric heating or high-voltage electric arc to reach a temperature of 1300-1500°C.

[0018] Optionally, in step S3, a nitric acid solution is used for the cleaning.

[0019] A nanofiber, wherein the nanofiber is prepared by the above preparation method.

[0020] An application of the aforementioned nanofiber in information transmission, catalysis, or sensors.

[0021] The method for preparing nanofibers according to a specific embodiment of the present invention involves using carbon nanotubes as templates, reacting a silicon source material on the carbon nanotubes to form a silicon carbide coating layer, and then oxidizing it to form a silicon oxide nanofiber. The nanofibers prepared by the method can have a diameter reduced to 20-100 nm and have high uniformity. Attached Figure Description

[0022] Figure 1 SEM image of silicon carbide-encapsulated carbon nanotubes in Example 1;

[0023] Figure 2 SEM image of the oxidized silicon oxide array in Example 1;

[0024] Figure 3 In Example 1, SEM image of the cleaned silica nanofiber array. Detailed Implementation

[0025] The present invention provides a method for preparing nanofibers, comprising the following steps:

[0026] S1: Coating step, in which a silicon source material reacts with a carbon source material including carbon nanotubes to form a silicon carbide coating layer on the surface of the carbon nanotubes;

[0027] S2: Oxidation step, in which the carbon nanotubes after the coating step are oxidized to silicon carbide to silicon oxide;

[0028] S3: Cleaning step, cleaning the carbon nanotubes after the oxidation step to obtain the nanofiber.

[0029] The method for preparing nanofibers according to a specific embodiment of the present invention firstly uses carbon nanotubes as templates, and a silicon source material is reacted on the carbon nanotubes to form a silicon carbide coating layer. When the silicon source material reacts on the carbon nanotubes to form the silicon carbide coating layer, since the carbon nanotubes can also serve as carbon source material, the silicon carbide coating layer formed is tightly bonded to the surface of the carbon nanotubes. Then, through further oxidation reaction, silicon oxide nanofibers with a diameter that can be reduced to 20-100 nm and high uniformity can be prepared.

[0030] In some specific embodiments of the present invention, the carbon nanotubes after the coating step are carbon nanotube arrays, and the final prepared nanofibers are nanofiber arrays. The carbon nanofiber arrays have a small diameter, enabling single-mode transmission of light source signals. In fields requiring specific photocatalysis, no filter is needed, achieving highly efficient monochromatic light catalysis. Furthermore, it has broad application prospects in information transmission, catalysis, and sensor fields.

[0031] In some specific embodiments of the present invention, the method for preparing nanofibers can use a carbon nanotube array as a template for coating, thereby ensuring that the carbon nanotubes after the coating step are a carbon nanotube array. In other specific embodiments, after a silicon carbide coating layer is formed on the surface of the carbon nanotubes, the carbon nanotubes forming the silicon carbide coating layer are oriented by external force to form a carbon nanotube array. For example, the carbon nanotube powder forming the silicon carbide coating layer is pressed into a long strip, external force is applied to both ends of the strip, and then the carbon nanotube array is formed by instantaneous heating using electric heating or a high-voltage arc. This method is more conducive to the formation of the carbon nanotube array. The carbon nanotubes after the coating step are carbon nanotube arrays. Specifically, for example, silicon carbide-coated carbon nanotube powder is dispersed in an ethanol solution, pressed into strips 10-15 cm long, 0.5-1 cm wide, and 1-2 mm thick, dried, graphite electrodes are attached to both ends of the strips and placed in a quartz tube, and an inert gas is passed through the quartz tube for a period of time, for example, 20-30 minutes. After the air is removed, a certain force, for example, 1-3 N, is applied to both ends of the strips. Then, electric heating or a high-voltage arc is used to instantly raise the temperature of the strips to 900-1000°C and maintain it for 5-10 seconds to prepare a silicon carbide-coated carbon nanotube array.

[0032] The method for preparing nanofibers according to specific embodiments of the present invention includes, in some specific embodiments, the S1: coating step comprising the steps of S11: coating with silicon source material and S12: reacting silicon source material to generate silicon carbide. The S11: coating with silicon source material comprises forming a resin coating layer with silicon source material on the surface of carbon nanotubes by forming silicon source material, carbon nanotubes and resin. Specifically, for example, silicon source material, carbon nanotubes and resin are mixed, and the resin is cured to form a resin coating layer with silicon source material on the surface of carbon nanotubes. In some specific embodiments, by weight, the silicon source material is 4 to 6 parts by weight, the carbon nanotubes are 2 to 3 parts by weight, and the resin is 50 to 60 parts by weight. S12: The step of reacting silicon source material to generate silicon carbide includes oxidizing carbon nanotubes with a resin coating layer of silicon source material on their surface. For example, in some embodiments, the silicon source material is oxidized to form a silicon carbide coating layer at a temperature of 1300-1500°C in an inert atmosphere. In some embodiments, the silicon source material is oxidized to form a silicon carbide coating layer at a temperature of 1300-1500°C in an inert atmosphere containing a carbon source gas, such as nitrogen, argon, or helium. The carbon source gas can be an olefin, such as ethylene, an alkyne, such as acetylene, an alkane, such as methane, or an aromatic hydrocarbon, such as benzene, and is particularly preferred to be acetylene. In some embodiments, the volume percentage of the carbon source gas in the inert atmosphere is 1-10%, more specifically 3-5%.

[0033] In some specific embodiments of the present invention, the resin used in the preparation method of the nanofiber is a thermosetting resin, and in other specific embodiments, the thermosetting resin is a phenolic resin. The silicon source material, carbon nanotubes and thermosetting resin solution are mixed and cured by heating, so that a thermosetting resin coating layer with silicon source material can be formed on the surface of the carbon nanotubes.

[0034] In some specific embodiments of the preparation method of the nanofiber of the present invention, the silicon source material is silicon powder or diatomaceous earth.

[0035] In some specific embodiments of the nanofiber preparation method of the present invention, in step S2, the oxidation is carried out in an oxygen atmosphere by electric heating or high-voltage electric arc to reach a temperature of 1300-1500°C. For example, oxygen is introduced into a quartz tube containing a carbon nanotube array wrapped with silicon carbide for 30-45 minutes to fill the tube with oxygen. Then, electric heating or high-voltage electric arc is used to instantly raise the temperature of the strip to 1300-1500°C and maintain it for 10-15 seconds, thereby oxidizing silicon carbide into silicon oxide.

[0036] In some specific embodiments of the nanofiber preparation method of the present invention, in step S3, a nitric acid solution is used for cleaning to remove residual impurities from the carbon nanotubes in the silica fiber array after the reaction. For example, the carbon nanotubes after the oxidation step are subjected to electrochemical cycling at 50V for 500-1000 cycles in a 3-5 mol / L nitric acid solution. In some specific embodiments, the cleaning further includes ultrasonic cleaning with water. For example, after cleaning with nitric acid solution, the nanofibers are placed in deionized water and ultrasonically cleaned for 10 minutes 5-8 times, and then dried at about 60°C.

[0037] In some specific embodiments of the preparation method of the nanofiber of the present invention, in the S1: coating step, in addition to silicon source material, carbon nanotubes and resin components, other substances may be added according to the actual application, such as rare earth metal elements that are subsequently modified by silicon oxide doping.

[0038] A specific embodiment of the present invention also provides a nanofiber, which is prepared by the above preparation method. In some specific embodiments, the diameter of the nanofiber is 20-100 nm.

[0039] The present invention also provides an application of the above-mentioned nanofiber, such as applications in fields such as information transmission, photocatalytic lighting, or sensors.

[0040] The present invention will be further illustrated by specific embodiments below.

[0041] Example 1

[0042] First, 2 parts by weight of carbon nanotubes, 50 parts by weight of phenolic resin, and 4 parts by weight of silicon powder were mixed at 350 RPM for 2 hours, then dried at 120℃ for 24 hours. All raw materials were then ground in an agate mortar for 30 minutes and cured in a muffle furnace at 200℃ for 6 hours. Finally, the prepared sample was placed in a tube furnace and heated to 1300℃ at a heating rate of 3℃ / min under an atmosphere of 95 parts by volume of argon and 5 parts by volume of acetylene gas, and held for 2.5 hours to obtain silicon carbide-coated carbon nanotubes. The silicon carbide-coated carbon nanotubes were observed under a scanning electron microscope as follows: Figure 1 As shown.

[0043] The silicon carbide-coated carbon nanotube powder was dispersed in an ethanol solution, pressed into a strip 10 cm long, 0.5 cm wide, and 1 mm thick, and dried at 60°C for 6 hours. Graphite electrodes were attached to both ends of the strip and placed in a quartz tube 20 cm long and 1.5 cm in diameter. Argon gas was introduced into the quartz tube for 20 minutes. After the air was removed, a force of 1 N was applied to both ends of the strip. Then, electric heating was used to instantly raise the temperature of the strip to 900°C and hold it for 5 seconds, forming a silicon carbide-coated carbon nanotube array.

[0044] The forces at both ends of the silicon carbide-encapsulated carbon nanotube array were released, and oxygen was introduced into a quartz tube for 30 minutes to fill the tube. Then, electric heating was used to instantaneously raise the temperature of the strip to 1300°C and hold it for 15 seconds, oxidizing the silicon carbide to silicon oxide. The oxidized silicon oxide nanofiber array was then observed using a scanning electron microscope as follows: Figure 2 As shown.

[0045] The obtained long, oxidized silica nanofiber arrays were subjected to electrochemical cycling at 50V for 500 cycles in a 3 mol / L nitric acid solution. Then, they were immersed in deionized water, ultrasonically cleaned five times for 10 min each, and dried at 60°C for 12 h. The cleaned silica nanofiber arrays were observed using a scanning electron microscope as follows: Figure 3 As shown.

[0046] Example 2

[0047] First, 3 parts by weight of carbon nanotubes, 60 parts by weight of phenolic resin, and 6 parts by weight of diatomaceous earth were mixed at 350 RPM for 4 hours, and then dried at 120℃ for 24 hours. All raw materials were ground in an agate mortar for 60 minutes and cured in a muffle furnace at 200℃ for 6 hours. Finally, the prepared sample was placed in a tube furnace and heated to 1500℃ at a heating rate of 3℃ / min under an atmosphere of 97 parts by volume of argon and 3 parts by volume of acetylene gas, and held at that temperature for 3.5 hours to obtain carbon nanotubes encapsulated with silicon carbide.

[0048] The silicon carbide-coated carbon nanotube powder was dispersed in an ethanol solution, pressed into a strip 15 cm long, 1 cm wide, and 2 mm thick, and dried at 60°C for 6 hours. Graphite electrodes were attached to both ends of the strip and placed in a quartz tube 20 cm long and 1.5 cm in diameter. Nitrogen gas was introduced into the quartz tube for 30 minutes. After the air was removed, a force of 3 N was applied to both ends of the strip. Then, a high-voltage electric arc was used to instantly raise the temperature of the strip to 1000°C and hold it for 10 seconds, forming a silicon carbide-coated carbon nanotube array.

[0049] The forces at both ends of the carbon nanotube array encapsulated in silicon carbide were released, and oxygen was introduced into the quartz tube for 45 minutes to fill the tube with oxygen. Then, electric heating was used to instantly raise the temperature of the strip to 1500°C and hold it for 15 seconds, thus oxidizing the silicon carbide into silicon oxide.

[0050] The obtained long, oxidized silica nanofiber array was subjected to electrochemical cycling at 50V for 1000 cycles in a 5 mol / L nitric acid solution. Then, it was placed in deionized water, ultrasonically cleaned 8 times for 10 min each, and dried at 60°C for 12 h. The results of scanning electron microscopy (SEM) observation of the cleaned silica nanofiber array (figure omitted) were similar to those in Example 1.

[0051] Example 3

[0052] First, 1.5 parts by weight of carbon nanotubes, 55 parts by weight of phenolic resin, and 5 parts by weight of silicon powder were mixed at 350 RPM for 3 hours, and then dried at 120°C for 24 hours. All raw materials were ground in an agate mortar for 40 minutes and cured in a muffle furnace at 200°C for 6 hours. Finally, the prepared sample was placed in a tube furnace and heated to 1400°C at a heating rate of 3°C / min under an atmosphere of 96 parts by volume of argon and 4 parts by volume of acetylene gas, and held for 3 hours to obtain carbon nanotubes encapsulated in silicon carbide.

[0053] The silicon carbide-coated carbon nanotube powder was dispersed in an ethanol solution, pressed into a strip 10 cm long, 0.5 cm wide, and 2 mm thick, and dried at 60°C for 6 hours. Graphite electrodes were attached to both ends of the strip, which was then placed in a quartz tube 20 cm long and 1.5 cm in diameter. Argon gas was introduced into the quartz tube for 20 minutes to purge the air. A 200 g weight was then hung at the bottom of the strip, and a high-voltage electric arc was used to instantly raise the temperature of the strip to 950°C and hold it for 10 seconds, thus forming a silicon carbide-coated carbon nanotube array.

[0054] The forces at both ends of the carbon nanotube array wrapped in silicon carbide were released, and oxygen was introduced into the quartz tube for 30 minutes to fill the tube with oxygen. Then, electric heating was used to instantly raise the temperature of the strip to 1400°C and hold it for 15 seconds, thus oxidizing the silicon carbide into silicon oxide.

[0055] The obtained long, oxidized silica nanofiber array was subjected to electrochemical cycling at 50V for 800 cycles in a 5 mol / L nitric acid solution. Then, it was placed in deionized water, ultrasonically cleaned five times for 10 min each, and dried at 60°C for 12 h. The results of scanning electron microscopy (SEM) observation of the cleaned silica nanofiber array (figure omitted) were similar to those in Example 1.

[0056] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method of fabricating a nanofiber, comprising: The method comprises the following steps: S1: a coating step, in which a silicon source substance is reacted with a carbon source substance comprising carbon nanotubes to form a silicon carbide coating layer on the surface of the carbon nanotubes, the carbon nanotubes with the silicon carbide coating layer are pressed into a long strip, an external force is applied to both ends of the long strip, and the carbon nanotubes with the silicon carbide coating layer are formed into a carbon nanotube array by means of instantaneous heating by electric heating or high-voltage arc; S2: an oxidation step, in which the carbon nanotube array after the coating step is subjected to an oxidation reaction to oxidize the silicon carbide into silicon oxide; S3: a cleaning step, in which the carbon nanotube array after the oxidation step is cleaned to obtain the nano optical fiber.

2. The production method according to claim 1, characterized by, In the S1 step, a resin coating layer with a silicon source substance is formed on the surface of the carbon nanotubes by using a silicon source substance, carbon nanotubes and resin, and then the silicon carbide coating layer is formed at a temperature of 1300-1500°C in an inert atmosphere or an inert atmosphere with a carbon source gas.

3. The production method according to claim 2, characterized by, The resin is a thermosetting resin.

4. The production method according to claim 3, characterized by, The thermosetting resin is a phenolic resin.

5. The preparation method according to claim 2, characterized in that, The silicon source substance is 4-6 parts by weight, the carbon nanotubes are 2-3 parts by weight, and the resin is 50-60 parts by weight.

6. The preparation method according to claim 2, characterized in that, The carbon source gas is acetylene.

7. The preparation method according to claim 1, characterized in that, The silicon source substance is silicon powder or diatomite.

8. The method of claim 1, wherein, In the S2 step, the oxidation is performed by using electric heating or high-voltage arc to reach a temperature of 1300-1500°C in an oxygen atmosphere.

9. The method of claim 1, wherein, In the S3 step, the cleaning is performed by using a nitric acid solution.

10. A nanofiber, characterized by, The nano optical fiber is prepared by any one of the preparation methods in claims 1-9.

11. Use of the nano optical fiber of claim 10 in information transmission, catalysis or sensors.

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