Crack-modified hollow carbon nanowires and methods of making the same

Abstract

The application belongs to the technical field of inorganic nonmetallic materials, and particularly relates to a crack-modified hollow carbon nanowire and a preparation method thereof. The preparation method comprises the following steps: mixing and stirring polyacrylonitrile, acetylacetone, dimethylformamide and aluminum oxide to obtain a shell spinning solution; mixing and stirring polystyrene and dimethylformamide to obtain a core spinning solution; performing coaxial electrospinning on the shell spinning solution and the core spinning solution to collect a fiber membrane; sequentially performing pre-oxidation and carbonization on the fiber membrane to obtain a hollow carbon nanowire; and performing hydrothermal reaction on the hollow carbon nanowire in an alkali solution to obtain the crack-modified hollow carbon nanowire. The inner surface of the prepared crack-modified hollow carbon nanowire is exposed, and the crack-modified hollow carbon nanowire can effectively play the advantages of a large specific surface area and a high loading rate, and has a wide application prospect in the fields of wave absorption, catalysis, electrochemical energy storage and the like. The raw materials are easy to obtain, the cost is low, the production equipment is relatively simple, the operation is convenient, and the industrial large-scale production can be easily realized.

Description

Technical Field

[0001] This invention belongs to the field of inorganic non-metallic materials technology, specifically relating to a crack-modified hollow carbon nanowire and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Carbon materials possess excellent electrical and thermal conductivity, as well as good chemical and thermal stability, making them widely applicable in fields such as microwave absorption, catalysis, and electrochemical energy storage. Among all carbon materials, carbon nanowires have attracted considerable attention from researchers due to their excellent aspect ratio and unique network structure.

[0004] Electrospinning is a commonly used method for preparing carbon nanowires. This method uses high voltage to spray and stretch a polymer solution within a nozzle, forming nanowires. Electrospinning also allows for the structural design of carbon nanowire morphology. Hollow carbon nanowires, in particular, have attracted significant attention due to their large specific surface area, controllable pore size distribution, abundant active sites, and excellent loading capacity. However, because hollow carbon nanowires only have unclosed channels at both ends, the inner surface in the middle is difficult to utilize, thus hindering the full realization of their advantages, such as large specific surface area and high loading rate. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a crack-modified hollow carbon nanowire and its preparation method. The invention utilizes coaxial electrospinning as the preparation method, obtaining hollow nanowires after pre-oxidation and carbonization treatments. Then, a crack modification method using an alumina hard template is employed, with a hydrothermal synthesis method used to corrode alumina to form surface cracks on the carbon nanowires, ultimately yielding crack-modified hollow carbon nanowires. This preparation method offers advantages such as stability, reliability, simple operation, low equipment cost, and readily available raw materials.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing crack-modified hollow carbon nanowires, comprising the following steps:

[0008] S1. Polyacrylonitrile, acetylacetone, dimethylformamide and alumina are mixed and stirred to obtain shell spinning solution;

[0009] S2. Mix and stir polystyrene and dimethylformamide to obtain a nuclear spinning solution;

[0010] S3. Coaxial electrospinning of the shell spinning solution and the core spinning solution is performed to collect the fiber membrane.

[0011] S4. The fiber membrane is pre-oxidized and carbonized sequentially to obtain hollow carbon nanowires;

[0012] S5. Hollow carbon nanowires are subjected to hydrothermal reaction in an alkaline solution to obtain crack-modified hollow carbon nanowires.

[0013] Preferably, the mass ratio of polyacrylonitrile, acetylacetone, dimethylformamide, and alumina is 1–3:1–3:5–15:0.1–0.5; the mass ratio of polystyrene and dimethylformamide is 1–5:5–15; and the mass ratio of shell spinning solution to nucleus spinning solution is 1:0.75–0.85.

[0014] Preferably, the stirring temperature in step S1 is 70-90°C and the stirring time is 10-16 hours.

[0015] Preferably, the stirring temperature in step S2 is 70-90°C and the stirring time is 10-16 hours.

[0016] Preferably, the electrospinning temperature is 20–50℃, the voltage is 10–15kV, the feed rate is 0.001–0.01mm / s, the roller speed is 300–500r / min, and the spinning time is 10–20h.

[0017] Preferably, the pre-oxidation temperature is 250–350°C, the heating rate is 1–3°C / min, the holding time is 1–3 h, and the atmosphere is air.

[0018] Preferably, the carbonization temperature is 600–900℃, the heating rate is 5–10℃ / min, the holding time is 2–5h, and the atmosphere is argon.

[0019] Preferably, the alkaline solution is a sodium hydroxide or potassium hydroxide solution with a concentration of 1 to 6 M.

[0020] Preferably, the hydrothermal reaction temperature is 120–180℃ and the hydrothermal time is 6–12 hours.

[0021] In a further preferred embodiment, after the hydrothermal reaction is completed, the reaction product is washed 3 to 5 times by centrifugation and then dried.

[0022] In a further preferred embodiment, the centrifugation speed is 4000-5000 r / min, the drying temperature is 60-90℃, and the drying time is 8-16 h.

[0023] In a second aspect, the present invention provides a crack-modified hollow carbon nanowire, which is obtained by the preparation method described in the first aspect.

[0024] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0025] The crack-modified hollow carbon nanowires prepared in this invention expose the inner surface of the hollow carbon nanowires through crack modification, which can effectively give full play to the advantages of large specific surface area and high loading rate, and have broad application prospects in the fields of microwave absorption, catalysis, and electrochemical energy storage.

[0026] The raw materials used in the preparation method of the present invention are readily available and low in cost, and the production equipment is relatively simple, easy to operate, and easy to scale up for industrial production. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 This is a low-magnification scanning electron microscope image of hollow carbon nanowires from Example 1 of the present invention;

[0029] Figure 2 This is a high-magnification scanning electron microscope image of hollow carbon nanowires from Example 1 of the present invention;

[0030] Figure 3 The images show a low-magnification scanning electron microscope (SEM) image (left) and an EDS image (right) of the crack-modified hollow carbon nanowires of Example 1 of the present invention.

[0031] Figure 4 This is a high-magnification scanning electron microscope image of the crack-modified hollow carbon nanowires of Example 1 of the present invention;

[0032] Figure 5 The Raman spectrum of the crack-modified hollow carbon nanowires of Example 1 of the present invention;

[0033] Figure 6 This is a pore size distribution diagram of the crack-modified hollow carbon nanowires of Example 1 of the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0035] Example 1

[0036] Weigh 2.5g of polyacrylonitrile, 3.0g of acetylacetone, 10.0g of dimethylformamide and 0.2g of alumina, and stir magnetically for 10h in a water bath at 80℃ to obtain shell spinning solution.

[0037] Weigh 2.5g of polystyrene and 10.0g of dimethylformamide, and stir magnetically for 10h in a water bath at 80℃ to obtain the nuclear spinning solution.

[0038] The shell spinning solution and the core spinning solution were added to two separate syringes. Coaxial electrospinning was performed using 22G / 17G needles. The fiber membrane was collected using aluminum foil covering the rollers. The spinning temperature was 40℃, the voltage was 10kV, the feed rate was 0.002mm / s, the roller speed was 400r / min, and the spinning time was 16h.

[0039] The spun membrane was placed in a resistance furnace and pre-oxidized in air at a temperature of 250℃, a heating rate of 2℃ / min, and a holding time of 1 h. The pre-oxidized spun membrane was then placed in a tube furnace and carbonized in argon at a temperature of 700℃, a heating rate of 10℃ / min, and a holding time of 2 h to obtain hollow carbon nanowires.

[0040] Hollow carbon nanowires were transferred to a hydrothermal reactor with 50 mL of 1 M potassium hydroxide solution and heated to 140 °C for 10 h. After the hydrothermal reaction, the reaction product was washed three times by centrifugation at 4000 r / min, and finally dried at 80 °C for 12 h to obtain crack-modified hollow carbon nanowires.

[0041] like Figure 1 As shown in the scanning electron microscope images, the diameter of the hollow carbon nanowires is 1–2 micrometers. Figure 2 As shown, hollow carbon nanowires exhibit a distinct hollow structure. For example... Figure 3 As shown in the scanning electron microscope (SEM) images, the diameter of the crack-modified hollow carbon nanowires is 1–2 micrometers, and the cracks are obvious and continuous. EDS images show that the crack-modified hollow carbon nanowires contain only carbon, and the alumina is completely etched away. Figure 4 As shown, the crack-modified hollow carbon nanowires exhibit obvious cracks, exposing the inner surface and increasing the specific surface area. Figure 5 As shown, the Raman spectrum of the crack-modified hollow carbon nanowires exhibits obvious D and G peaks, proving that they possess a good degree of graphitization. Figure 6 As shown, the specific surface area of ​​the crack-modified hollow carbon nanowires is 99.2 m². 2 / g indicates that it has a large specific surface area.

[0042] Example 2

[0043] Weigh 1.8g polyacrylonitrile, 2.4g acetylacetone, 8.0g dimethylformamide and 0.1g alumina, and stir magnetically for 10h in a water bath at 70℃ to obtain shell spinning solution.

[0044] Weigh 2.0g of polystyrene and 8.0g of dimethylformamide, and stir magnetically for 10h in a water bath at 70℃ to obtain the nuclear spinning solution.

[0045] The shell spinning solution and the core spinning solution were added to two separate syringes. Coaxial electrospinning was performed using 22G / 17G needles. The fiber membrane was collected using aluminum foil covering the rollers. The spinning temperature was 30℃, the voltage was 12kV, the feed rate was 0.001mm / s, the roller speed was 350r / min, and the spinning time was 10h.

[0046] The spun membrane was placed in a resistance furnace and pre-oxidized in air at a temperature of 300℃, a heating rate of 3℃ / min, and a holding time of 2 hours. The pre-oxidized membrane was then placed in a tube furnace and carbonized in argon at a temperature of 800℃, a heating rate of 10℃ / min, and a holding time of 3 hours to obtain hollow carbon nanowires.

[0047] Hollow carbon nanowires were transferred to a hydrothermal reactor with 50 mL of 2M potassium hydroxide solution and heated to 160 °C for 10 h. After the hydrothermal reaction, the reaction product was washed three times by centrifugation at 4800 r / min, and finally dried at 80 °C for 10 h to obtain crack-modified hollow carbon nanowires.

[0048] Example 3

[0049] Weigh 3.0g polyacrylonitrile, 3.0g acetylacetone, 15.0g dimethylformamide and 0.5g alumina, and magnetically stir in a water bath at 90℃ for 16h to obtain shell spinning solution.

[0050] Weigh 5.0g of polystyrene and 15.0g of dimethylformamide, and stir magnetically for 16h in a water bath at 90℃ to obtain the nuclear spinning solution.

[0051] The shell spinning solution and the core spinning solution were added to two separate syringes. Coaxial electrospinning was performed using 22G / 17G needles. The fiber membrane was collected using aluminum foil covering the rollers. The spinning temperature was 50℃, the voltage was 15kV, the feed rate was 0.005mm / s, the roller speed was 500r / min, and the spinning time was 20h.

[0052] The spun membrane was placed in a resistance furnace and pre-oxidized in air at a temperature of 350℃, a heating rate of 3℃ / min, and a holding time of 1 h. The pre-oxidized membrane was then placed in a tube furnace and carbonized in argon at a temperature of 900℃, a heating rate of 10℃ / min, and a holding time of 2 h to obtain hollow carbon nanowires.

[0053] Hollow carbon nanowires were transferred to a hydrothermal reactor with 50 mL of 6M potassium hydroxide solution and heated to 180 °C for 6 h. After the hydrothermal reaction, the reaction product was washed three times by centrifugation at 5000 r / min, and finally dried at 90 °C for 8 h to obtain crack-modified hollow carbon nanowires.

[0054] Example 4

[0055] Weigh 1.0g polyacrylonitrile, 1.0g acetylacetone, 5.0g dimethylformamide and 0.1g alumina, and magnetically stir for 16h in a water bath at 70℃ to obtain shell spinning solution.

[0056] Weigh 1.0g of polystyrene and 5.0g of dimethylformamide, and stir magnetically for 16h in a water bath at 70℃ to obtain the nuclear spinning solution.

[0057] The shell spinning solution and the core spinning solution were added to two separate syringes. Coaxial electrospinning was performed using 22G / 17G needles. The fiber membrane was collected using aluminum foil covering the rollers. The spinning temperature was 20℃, the voltage was 15kV, the feed rate was 0.01mm / s, the roller speed was 300r / min, and the spinning time was 10h.

[0058] The spun membrane was placed in an electric resistance furnace and pre-oxidized in air at a temperature of 250℃, a heating rate of 2℃ / min, and a holding time of 3 hours. The pre-oxidized membrane was then placed in a tube furnace and carbonized in argon at a temperature of 600℃, a heating rate of 5℃ / min, and a holding time of 5 hours to obtain hollow carbon nanowires.

[0059] Hollow carbon nanowires were transferred to a hydrothermal reactor with 50 mL of 1 M potassium hydroxide solution and heated to 120 °C for 12 h. After the hydrothermal reaction, the reaction product was washed three times by centrifugation at 4000 r / min, and finally dried at 60 °C for 16 h to obtain crack-modified hollow carbon nanowires.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing crack-modified hollow carbon nanowires, characterized in that, Includes the following steps: S1. Polyacrylonitrile, acetylacetone, dimethylformamide and alumina are mixed and stirred to obtain shell spinning solution; S2. Mix and stir polystyrene and dimethylformamide to obtain a nuclear spinning solution; S3. Coaxial electrospinning of the shell spinning solution and the core spinning solution is performed to collect the fiber membrane. S4. The fiber membrane is pre-oxidized and carbonized sequentially to obtain hollow carbon nanowires; S5. Hollow carbon nanowires are hydrothermally reacted in an alkaline solution to obtain crack-modified hollow carbon nanowires. The mass ratio of polyacrylonitrile, acetylacetone, dimethylformamide, and alumina is 1~3:1~3:5~15:0.1~0.5; the mass ratio of polystyrene and dimethylformamide is 1~5:5~15; and the mass ratio of shell spinning solution and core spinning solution is 1:0.75~0.

85.

2. The preparation method according to claim 1, characterized in that, In step S1, the stirring temperature is 70~90 ℃ and the stirring time is 10~16 h.

3. The preparation method according to claim 1, characterized in that, In step S2, the stirring temperature is 70~90 ℃ and the stirring time is 10~16 h.

4. The preparation method according to claim 1, characterized in that, The electrospinning temperature is 20~50 ℃, the voltage is 10~15 kV, the feed rate is 0.001~0.01 mm / s, the roller speed is 300~500 r / min, and the spinning time is 10~20 h.

5. The preparation method according to claim 1, characterized in that, The pre-oxidation temperature is 250~350 ℃, the heating rate is 1~3 ℃ / min, the holding time is 1~3 h, and the atmosphere is air.

6. The preparation method according to claim 1, characterized in that, The carbonization temperature is 600~900 ℃, the heating rate is 5~10 ℃ / min, the holding time is 2~5 h, and the atmosphere is argon.

7. The preparation method according to claim 1, characterized in that, The alkaline solution is a solution containing sodium hydroxide or potassium hydroxide, with a concentration of 1~6 M.

8. The preparation method according to claim 1, characterized in that, The hydrothermal reaction temperature is 120~180 ℃, and the hydrothermal time is 6~12 h.

9. The preparation method according to claim 8, characterized in that, After the hydrothermal reaction is complete, the reaction product is washed 3 to 5 times by centrifugation and then dried.

10. The preparation method according to claim 9, characterized in that, The centrifugation speed is 4000~5000 r / min, the drying temperature is 60~90 ℃, and the drying time is 8~16h.

11. A crack-modified hollow carbon nanowire, characterized in that, Obtained by the preparation method as described in any one of claims 1-10.

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