Preparation method of flexible carbon nanofiber membrane without pre-oxidation

Abstract

The invention belongs to the technical field of functional nanofiber membranes, and relates to a preparation method of a flexible carbon nanofiber membrane without pre-oxidation. The preparation method comprises the following steps: adding anhydrous zinc acetate and tetraethyl orthosilicate into N, N-dimethylformamide, uniformly mixing, then adding polyacrylonitrile, and stirring until uniformly mixing to obtain a spinning solution; and performing electrostatic spinning on the spinning solution to obtain a as-spun nanofiber membrane, and calcining the as-spun nanofiber membrane in an argon atmosphere to obtain the flexible carbon nanofiber membrane. Compared with the traditional preparation process of the flexible carbon nanofiber membrane, the method provided by the invention has the advantages that the step of pre-oxidation can be omitted, the method is simple, the process is simple and convenient, the energy consumption is effectively reduced, and the method has a good application prospect. The prepared flexible carbon nanofiber membrane has good mechanical performance, is not obviously damaged after being folded for multiple times, can bear a certain degree of tension, and is suitable for various application scenes.

Description

Technical Field

[0001] This invention belongs to the field of functional nanofiber membrane technology, and relates to a method for preparing a flexible carbon nanofiber membrane without pre-oxidation. Background Technology

[0002] Carbon nanofiber membranes possess three-dimensional porous networks, high specific area, and excellent heat and corrosion resistance, leading to widespread interest in environmental, energy, and catalysis fields. Current techniques for preparing carbon nanofiber membranes include template methods, electrospinning, and chemical vapor deposition. Electrospinning combined with high-temperature calcination provides a simple and efficient way to prepare structurally tunable carbon nanofiber membranes. However, the inherent brittleness of carbon nanofiber membranes limits their widespread application.

[0003] Patent CN120789946A reports an electrospinning process combined with freeze-drying-pre-oxidation-carbonization, introducing fluorine or zirconium oxide modified materials into the carbon nanofiber matrix to overcome defects in carbon nanofibers and improve the mechanical strength of the carbon nanofiber membrane. Patent CN120083011A reports an electrospinning process combined with hot pressing followed by pre-oxidation and carbonization, yielding a carbon nanofiber membrane with good flexibility, conductivity, and high battery power density. However, these preparation methods generally suffer from cumbersome processes and high energy consumption, with the pre-oxidation step being the most time-consuming and energy-intensive critical step in the entire process. Summary of the Invention

[0004] This invention addresses the time-consuming and energy-intensive pre-oxidation process in the traditional preparation of flexible carbon nanofiber membranes by proposing a method for preparing flexible carbon nanofiber membranes that does not require pre-oxidation.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution: A method for preparing a flexible carbon nanofiber membrane without pre-oxidation, comprising the following steps: (1) Add anhydrous zinc acetate and tetraethyl orthosilicate to N,N-dimethylformamide, mix well, then add polyacrylonitrile and stir until well mixed to obtain a spinning solution.

[0006] (2) Electrospinning the spinning solution to obtain a primary spun nanofiber membrane.

[0007] (3) The spun nanofiber membrane was calcined under an argon atmosphere to obtain a flexible carbon nanofiber membrane.

[0008] As a preferred option, the weight proportions of the substances in step (1) are as follows: 2-4 parts of polyacrylonitrile, 1-3 parts of tetraethyl orthosilicate, 1-2 parts of anhydrous zinc acetate, and 20-23 parts of N,N-dimethylformamide; the stirring time is 6-12 hours, and the stirring and mixing temperature is 55-65℃.

[0009] As a preferred option, the electrospinning conditions in step (2) are: humidity of 36-42%, temperature of 20-28℃, electrostatic voltage of 13.5-15.5kV, distance from the tip of the spinning needle to the collector of 140-210mm, and injection speed of 1.0-1.5mL / h.

[0010] Preferably, in step (3), the calcination temperature is 600-800℃, the heating rate is 1-5℃ / min, the holding time at the calcination temperature is 1-2h, and the calcination atmosphere is argon.

[0011] The present invention proposes a flexible carbon nanofiber membrane prepared by the above method.

[0012] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. Compared with the traditional preparation process of flexible carbon nanofiber membranes, the method proposed in this invention can omit the pre-oxidation step, which is simple, convenient, effectively reduces energy consumption, and is environmentally friendly, thus having good prospects for industrial application.

[0013] 2. The flexible carbon nanofiber membrane prepared by this invention has good mechanical properties, does not suffer significant damage after multiple folds, and can withstand a certain degree of tensile force, making it suitable for various application scenarios. Attached Figure Description

[0014] Figure 1 This is a SEM characterization image of the flexible carbon nanofiber membrane in Example 1.

[0015] Figure 2 The figures show the flexibility and strength test results of the flexible carbon nanofiber membrane in Example 1. Detailed Implementation

[0016] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0017] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0018] In the following examples, some of the substances are manufactured or have the specified specifications. Unless otherwise specified, all other substances are conventional reagents used in chemical and chemical engineering experiments.

[0019] Polyacrylonitrile (PAN): Average molecular weight (Mw=150000), Shanghai Maclean Biochemical Technology Co., Ltd.

[0020] Anhydrous zinc acetate: content (99%), Aladdin Reagent (Shanghai) Co., Ltd.

[0021] Tetraethyl orthosilicate: Content (≥28.4% as SiO2), Sinopharm Chemical Reagent Co., Ltd.

[0022] N,N-Dimethylformamide (DMF): Content (≥99.5%), Shanghai Lingfeng Chemical Reagent Co., Ltd.

[0023] In the following embodiments, the mechanical property testing process for the fiber membrane is as follows: A fiber membrane (3mm wide and 30mm long) was cut and its stress and elongation were tested and analyzed using a tensile strength tester (XQ-1C, Shanghai Xinxian Instrument Co., Ltd.). Test conditions: tensile speed 2mm / min, clamping distance 20mm. Young's modulus was calculated based on the stress-strain curve obtained from the test.

[0024] Example 1 This embodiment provides a specific process for producing a flexible carbon nanofiber membrane without a pre-oxidation step. 1.5 g of anhydrous zinc acetate and 2.2 mL of tetraethyl orthosilicate were added to 22 mL of N,N-dimethylformamide. The mixture was placed in an oil bath at 60°C and 40 rpm and stirred for 15 min. Then, 3.0 g of polyacrylonitrile was added, and stirring continued at a constant temperature of 60°C for 8 h at a stirring rate of 40 rpm, resulting in a clear and transparent spinning solution. The spinning solution was injected into a syringe, and electrospinning was performed under the following conditions: spinning humidity 38-40%, temperature 24-26°C, electrostatic voltage set to 13.5 kV, distance from the spinning needle tip to the collector 140 mm, and injection speed set to 1.0 mL / h, yielding a pre-spun nanofiber membrane. The obtained nanofiber membrane was placed in a tube furnace and calcined at high temperature under an argon atmosphere. The calcination temperature was 600℃, the heating rate was 2℃ / min, the holding time at 600℃ was 2h, the argon flow rate was 60mL / min, and the calcination was completed by natural cooling to room temperature to obtain a flexible carbon nanofiber membrane.

[0025] The flexible carbon nanofiber membrane prepared in this embodiment was tested and found to have an elongation of 1.6% and a Young's modulus of 90.8 MPa.

[0026] Example 2 Unless otherwise specified, the embodiments described in this example and the following examples are consistent with Example 1. 1.1 g of anhydrous zinc acetate and 2.2 mL of tetraethyl orthosilicate were added to 22 mL of N,N-dimethylformamide. The mixture was stirred at a constant temperature of 60°C for 15 min at a stirring rate of 40 rpm. Then, 3.0 g of polyacrylonitrile was added, and the mixture was stirred at 60°C and 40 rpm for 10 h to obtain a clear and transparent spinning solution. The spinning solution was injected into a syringe, and electrospinning was performed under the following conditions: spinning humidity 38-40%, temperature 24-26°C, electrostatic voltage set to 13.5 kV, distance from the spinning needle tip to the collector 180 mm, and injection speed set to 1.2 mL / h to obtain a preliminary spun nanofiber membrane. The obtained nanofiber membrane was placed in a tube furnace and calcined at high temperature under an argon atmosphere. The calcination temperature was 750℃, the heating rate was 5℃ / min, the holding time at 750℃ was 1.5h, the argon flow rate was 75mL / min, and after calcination, it was naturally cooled to room temperature to obtain a flexible carbon nanofiber membrane. The flexible carbon nanofiber membrane prepared in this example was tested and found to have an elongation of 1.4% and a Young's modulus of 99.5MPa.

[0027] Example 3 1.5 g of anhydrous zinc acetate and 1.8 mL of tetraethyl orthosilicate were added to 22 mL of N,N-dimethylformamide and stirred at a constant temperature of 60 °C for 15 min at a stirring speed of 40 rpm. Then, 3.0 g of polyacrylonitrile was added, and the mixture was stirred at 60 °C and 40 rpm for another 9 h to obtain a clear and transparent spinning solution. The spinning solution was injected into a syringe, and electrospinning was performed under the following conditions: spinning humidity 38-40%, temperature 24-26 °C, electrostatic voltage set to 13.5 kV, distance from the spinning needle tip to the collector 200 mm, and injection speed set to 1.5 mL / h to obtain a preliminary spun nanofiber membrane. The obtained nanofiber membrane was placed in a tube furnace and calcined at high temperature under an argon atmosphere. The calcination temperature was 650 °C, the heating rate was 5 °C / min, the holding time at 650 °C was 1 h, and the argon flow rate was 80 mL / min. After calcination, the membrane was naturally cooled to room temperature to obtain a flexible carbon nanofiber membrane. The flexible carbon nanofiber membrane prepared in this embodiment was tested and found to have an elongation of 1.2% and a Young's modulus of 113.5 MPa.

[0028] The flexible carbon nanofiber membrane prepared in Example 1 was characterized.

[0029] 1. SEM characterization The flexible carbon nanofiber membrane prepared in Example 1 was characterized by SEM, and the results are as follows: Figure 1 ,from Figure 1 It can be seen that the carbon nanofiber membrane exhibits a typical three-dimensional network morphology and the fibers are relatively uniform.

[0030] 2. Flexibility and strength performance testing The flexible carbon nanofiber membrane prepared in Example 1 was subjected to strength testing. Figure 2 a) and folding test ( Figure 2 (b) Testing showed that the carbon nanofiber membrane prepared in Example 1 could not only withstand a certain amount of tension, but also withstand multiple folds without damage, further demonstrating that the carbon nanofiber membrane has good mechanical properties.

[0031] Comparative Example 1 The difference between this comparative example and Example 1 is that anhydrous zinc acetate was not used; all other conditions and preparation processes were the same as in Example 1. Testing revealed that the obtained carbon nanofiber membrane was a brittle membrane with an elongation of 0.7% and a Young's modulus of 196.7 MPa. The flexibility of the carbon nanofiber membrane obtained in this comparative example was significantly less than that in Example 1.

[0032] Comparative Example 2 The difference between this comparative example and Example 1 is that tetraethyl orthosilicate was not added; the other conditions and preparation process were the same as in Example 1. Testing revealed that the obtained carbon nanofiber membrane was a brittle membrane with an elongation of 0.8% and a Young's modulus of 171.2 MPa. The flexibility of the carbon nanofiber membrane obtained in this comparative example was significantly less than that in Example 1.

[0033] Comparative Example 3 The difference between this comparative example and Example 1 is that tetraethyl orthosilicate and anhydrous zinc acetate are omitted. The remaining conditions and preparation process are the same as in Example 1. Testing showed that the prepared carbon nanofiber membrane was a brittle membrane with an elongation of 0.4% and a Young's modulus of 243.6 MPa. The flexibility of the carbon nanofiber membrane obtained in this comparative example is much less than that in Example 1. The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a flexible carbon nanofiber membrane without pre-oxidation, characterized in that, The steps are as follows: (1) Add anhydrous zinc acetate and tetraethyl orthosilicate to N,N-dimethylformamide, mix well, then add polyacrylonitrile and stir until well mixed to obtain a spinning solution; (2) Electrospinning the spinning solution to obtain a primary spun nanofiber membrane; (3) The spun nanofiber membrane was calcined under an argon atmosphere to obtain a flexible carbon nanofiber membrane.

2. The method for preparing a flexible carbon nanofiber membrane without pre-oxidation according to claim 1, characterized in that, The weight proportions of the substances in step (1) are as follows: 2-4 parts of polyacrylonitrile, 1-3 parts of tetraethyl orthosilicate, 1-2 parts of anhydrous zinc acetate, and 20-23 parts of N,N-dimethylformamide; the stirring time is 6-12 hours and the stirring temperature is 55-65℃.

3. The method for preparing a flexible carbon nanofiber membrane without pre-oxidation according to claim 1, characterized in that, In step (2), the electrospinning conditions are: humidity 36-42%, temperature 20-28℃, electrostatic voltage 13.5-15.5kV, distance from the tip of the spinning needle to the collector 140-210mm, and injection speed set to 1.0-1.5mL / h.

4. The method for preparing a flexible carbon nanofiber membrane without pre-oxidation according to claim 1, characterized in that, In step (3), the calcination temperature is 600-800℃, the heating rate is 1-5℃ / min, the holding time at the calcination temperature is 1-2h, and the calcination atmosphere is argon.

5. A flexible carbon nanofiber membrane, characterized in that, It is prepared by any one of the methods of claims 1-4.

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