Preparation Method of Silicon Carbide Flexible Fiber

Abstract

The preparation method of silicon carbide flexible fibers includes: grinding polycarbosilane into powder, mixing and stirring it with methanol, polyvinylpyrrolidone, N,N-dimethylformamide and chloroform to obtain a SiC precursor solution; adding ZIF-67 to the precursor solution and stirring to prepare an electrospinning solution, and then performing electrospinning; collecting the fibers obtained by electrospinning and transferring them to a muffle furnace at 150-300 °C for curing; placing the cured fibers in a high-temperature inert gas environment for pyrolytic carbonization. The present invention improves the problem of insufficient original flexibility of the ceramic material silicon carbide, and effectively improves the wave-absorbing performance of the material by doping ZIF-67. The prepared SiC-ZIF composite nanofibers have relatively good wave-absorbing performance when the thickness is 2.9 mm, and the minimum reflection loss can reach -52.65 dB. The present invention provides a method for improving the flexibility performance of silicon carbide ceramic materials, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorbing materials, and particularly relates to a preparation method of silicon carbide flexible fibers. Background Art

[0002] With the rapid development of modern electronic industry and wireless communication technology, the use of various electronic products has brought great convenience to our lives while also leading to an increasing electromagnetic pollution. On the one hand, the electromagnetic radiation generated by electronic devices will cause certain harm to human health; on the other hand, electromagnetic pollution will affect the communication in our daily life and even national defense and military. The problem of electromagnetic pollution has become an urgent problem to be solved in today's society. Therefore, it is very necessary to use wave-absorbing materials to protect our devices. A wave-absorbing material is a material that can convert the electromagnetic energy of electromagnetic waves into heat energy or other forms of energy through various ways to achieve the function of absorbing electromagnetic waves.

[0003] Due to its excellent chemical stability, high dielectric loss and low mass, carbon-based materials have always been a research hotspot in the field of electromagnetic wave absorption, such as graphene, carbon nanotubes, carbon nanowires and a series of their composites. It is worth noting that among them, silicon carbide has attracted the attention of many scientific researchers due to its low density, high temperature resistance, oxidation resistance and excellent mechanical properties in extreme environments. However, due to its relatively single loss mechanism, poor effect when used alone and difficult impedance matching regulation, and the poor flexibility and processing performance of ceramic wave-absorbing materials, these have greatly affected the application range of silicon carbide in the wave-absorbing field.

[0004] Therefore, there is an urgent need for a preparation method of a flexible silicon carbide fiber wave-absorbing material with integrated functions at present. Summary of the Invention

[0005] Object of the Invention: To overcome the above deficiencies, the object of the present invention is to provide a preparation method of silicon carbide flexible fibers, which solves the problems of low dielectric constant of non-magnetic silicon carbide, only weak dielectric loss effect on electromagnetic waves, lack of magnetic loss mechanism, and mechanical properties of the material itself.

[0006] To solve the above technical problems, the present invention provides a preparation method of silicon carbide flexible fibers, including:

[0007] Step S1: Take a first preset amount of polycarbosilane, put it into a mortar and grind it until it becomes powdery, and then dissolve it in chloroform. The mixture is denoted as solution A;

[0008] Step S2: Take a second preset amount of cobalt nitrate hexahydrate and 2-methylimidazole and dissolve them in methanol respectively for mixing, then magnetically stir the mixed solution, and after the stirring is completed, perform centrifugal washing on it to collect the final precipitate ZIF-67;

[0009] Step S3: Mix solution A and precipitate ZIF-67 and perform ultrasonic stirring. After the stirring is completed, mix it with a third preset amount of polyvinylpyrrolidone and N,N-dimethylformamide, and perform magnetic stirring on it to obtain a uniformly mixed precursor solution after the stirring is completed;

[0010] Step S4: Transfer the precursor solution to a 10 mL syringe equipped with a 21G spinneret. During the electrospinning process, set a preset distance between the spinneret and the collection substrate, set a preset spinning voltage and a preset solution feeding rate, and collect it with a drum collector using tin foil as the substrate to obtain fibers;

[0011] Step S5: Place the fibers in a muffle furnace and heat them up at a first preset heating rate for a first preset number of times to raise the temperature to 200 - 300 °C and keep it warm for 1 - 12 hours to cure the fibers;

[0012] Step S6: Place the cured fibers in a tube furnace and heat them up at a second preset heating rate for a second preset number of times to raise the temperature to 900 - 1300 °C and keep it warm for 5 - 24 hours under a preset gas atmosphere.

[0013] As a preferred embodiment of the present invention, in step S1, the first preset amount of polycarbosilane is 0.5 - 1.5 g, and the chloroform is 10 - 20 mL.

[0014] As a preferred embodiment of the present invention, in step S2, the second preset amount of cobalt nitrate hexahydrate is 5 - 15 mL, 2-methylimidazole is 2 - 10 mL, methanol is 10 - 30 mL, the magnetic stirring time is 2 - 24 hours, and the magnetic stirring speed is 1500 - 3000 revolutions per minute.

[0015] As a preferred embodiment of the present invention, in step S3, the third preset amount of polyvinylpyrrolidone is 0.5 - 1.5 g, N,N-dimethylformamide is 2 - 5 g, the magnetic stirring speed is 1500 - 3000 revolutions per minute, and the stirring time is 2 - 24 hours.

[0016] As a preferred embodiment of the present invention, in step S3, the molecular weight of polyvinylpyrrolidone is M.W = 130000 g / mol.

[0017] As a preferred embodiment of the present invention, in step S4, the preset distance between the spinneret and the collection substrate is 15 - 25 cm, the preset spinning voltage is 10 - 25 kV, and the preset solution feeding rate is 0.03 - 0.1 mL / min.

[0018] As a preferred embodiment of the present invention, in step S5, the first preset heating rate is 1-5 °C / min, the first heating temperature is 150-200 °C, and the second heating temperature is 200-300 °C.

[0019] As a preferred embodiment of the present invention, in step S6, the second heating rate is 1-5 °C / min, the first heating temperature is 200-300 °C, the second heating temperature is 600-900 °C, the third heating temperature is 900-1300 °C, and the heat preservation temperature is 900-1300 °C.

[0020] The present invention also provides a silicon carbide flexible fiber made by the described preparation method.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. Due to the relatively high aspect ratio of the fiber itself, the interlaced porous network structure between the fibers, and the connection points between the interlaced fibers, the silicon carbide fiber material is endowed with good flexibility that it originally did not have. At the same time, this structure also builds a good conductive network, thus improving the wave absorption performance.

[0023] 2. By introducing ZIF-67, the magnetic loss mechanism of the silicon carbide fiber is increased. Moreover, the introduction of the metal not only improves the problem that the impedance matching of silicon carbide itself is difficult to regulate, but also forms a good conductive network with the structure interlaced by the fiber itself, thereby improving the wave absorption performance of the composite material. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0025] Figure 1 It is the minimum reflection loss performance diagram of the fibers under different ZIF-67 contents and different pyrolysis temperatures provided by the embodiments of the present invention; among them, Figure 1 (a) is the minimum reflection loss diagram of the fibers in Example 1, Figure 1 (b) is the minimum reflection loss diagram of the fibers in Example 2, Figure 1 (c) is the minimum reflection loss diagram of the fibers in Example 3.

[0026] Figure 2 It is the SEM diagram of the fibers prepared under the conditions of adding 0.5 g of ZIF-67 and a pyrolysis temperature of 1000 °C provided by Example 2 of the present invention. Detailed Embodiments

[0027] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0028] Before preparation, at least the following preparation instruments and configurations should be prepared: a mortar and pestle, measuring instruments, solvent containers, stirring instruments, a magnetic stirrer, an ultrasonic stirrer, syringes, an electrospinning device, a drum collector, a muffle furnace, and a tube furnace.

[0029] Among them: the mortar and pestle are used for grinding materials; the measuring instruments are used for accurately weighing materials; the solvent containers are used for dissolving and storing solvents; the stirring instruments are used for mixing solutions; the magnetic stirrer is used for magnetic stirring at a speed of 1500 - 3000 r / min; the ultrasonic stirrer is used for ultrasonic stirring of the mixture; a 10 mL syringe equipped with a 21G spinneret; the electrospinning device is set with a distance of 15 - 25 cm between the spinneret and the collection substrate, a spinning voltage of 10 - 25 kV, and a solution feeding rate of 0.03 - 0.1 mL / min; the drum collector collects with a tin foil paper as the substrate; the muffle furnace has a heating rate of 1 - 5 °C / min, can be heated multiple times, and has a constant temperature function. The muffle furnace is first heated to 150 - 200 °C and the second time to 200 - 300 °C; the tube furnace has a heating rate of 1 - 5 °C / min, can be heated multiple times, and has a constant temperature function. The tube furnace is first heated from room temperature to 200 - 300 °C, the second time to 600 - 900 °C, and the third time to 900 - 1300 °C, and is kept warm in a nitrogen or argon atmosphere.

[0030] Refer to Figure 1 As shown, in Example 1, the preparation method of the silicon carbide flexible fiber involved, the method includes the following steps:

[0031] S1: Take 1 g of polycarbosilane, put it into a mortar and grind it until it becomes powdery, and then dissolve it in 10 mL of chloroform. The mixture is denoted as solution A.

[0032] S2: Ultrasonically stir the mixture of solution A and ZIF-67 at a speed of 3000 r / min. After the stirring is completed, mix it with 0.75 g of polyvinylpyrrolidone and 3.86 g of N,N-dimethylformamide, and perform magnetic stirring on it at 3000 r / min. After the stirring is completed, a precursor uniformly mixed solution is obtained.

[0033] S3: Transfer the precursor solution into a 10 mL syringe equipped with a 21G spinneret. During the electrospinning process, the distance between the spinneret and the collecting substrate is 15 cm, the spinning voltage is 20 kV, the feeding rate of the solution is 0.04 mL / min, and the collection is carried out using a drum collector with tin foil as the substrate.

[0034] S4: Place the collected fibers in a muffle furnace and heat them from room temperature to 150 °C at a heating rate of 2 °C / min, then heat them to 250 °C at a heating rate of 1 °C / min and hold for 3 h.

[0035] S5: Place the cured fibers in a tube furnace and heat them from room temperature to 250 °C at a heating rate of 2 °C / min, then to 700 °C at a heating rate of 1 °C / min, and then to 1000 °C at a heating rate of 2 °C / min, and hold for 5 h under an argon atmosphere.

[0036] The fibers prepared by this method are fibers without adding ZIF-67.

[0037] Through vector network analysis test, the minimum reflection loss diagram of the fibers as shown in Figure 1 (a) is obtained.

[0038] Refer to Figure 1 and Figure 2 As shown, in Example 2, the preparation method of the silicon carbide flexible fiber involved, the method includes the following steps:

[0039] S1: Take 1 g of polycarbosilane, put it into a mortar and grind it until it becomes powdery, then dissolve it in 10 mL of chloroform, and mark the mixture as solution A.

[0040] S2: Take 5 mL of cobalt nitrate hexahydrate and 3.5 mL of 2-methylimidazole and dissolve them in 10 mL of methanol respectively. Mix the two solutions, then magnetically stir the mixed solution for 2 - 24 h. After stirring, perform centrifugal washing on it, and collect the final precipitate ZIF-67 to obtain 0.5 g of precipitate.

[0041] S3: Mix solution A and ZIF-67 and perform ultrasonic stirring at a speed of 3000 r / min. After stirring, mix it with 0.75 g of polyvinylpyrrolidone and 3.86 g of N,N-dimethylformamide, and perform magnetic stirring at 3000 r / min. After stirring, obtain a uniformly mixed precursor solution.

[0042] S4: Transfer the precursor solution into a 10 mL syringe equipped with a 21G spinneret. During the electrospinning process, the distance between the spinneret and the collecting substrate is 15 cm, the spinning voltage is 20 kV, the feeding rate of the solution is 0.04 mL / min, and the collection is carried out using a drum collector with tin foil as the substrate.

[0043] S5: Place the collected fibers in a muffle furnace and heat them from room temperature to 150 °C at a heating rate of 2 °C / min, then heat them to 250 °C at a heating rate of 1 °C / min and hold for 3 h.

[0044] S6: Place the cured fibers in a tube furnace and heat them from room temperature to 250 °C at a heating rate of 2 °C / min, then heat them to 700 °C at a heating rate of 1 °C / min, and then heat them to 1000 °C at a heating rate of 2 °C / min, and hold for 5 h under a nitrogen atmosphere.

[0045] The fibers prepared by this method are fibers added with 0.5 g of ZIF-67 and having a pyrolysis temperature of 1000 °C.

[0046] Through vector network analysis testing and SEM structure characterization, the SEM images as shown in Figure 2 and the minimum reflection loss diagram of the fibers as shown in Figure 1 (b) are obtained.

[0047] Refer to Figure 1 shown. In Example 3, a preparation method of silicon carbide flexible fibers is involved. The method includes the following steps:

[0048] S1: Take 1 g of polycarbosilane, put it into a mortar and grind it until it becomes powdery, then dissolve it in 10 mL of chloroform, and record the mixture as solution A.

[0049] S2: Take 5 mL of cobalt nitrate hexahydrate and 3.5 mL of 2-methylimidazole and dissolve them in 10 mL of methanol respectively. Mix the two solutions, then magnetically stir the mixed solution for 2 - 24 h. After the stirring is completed, carry out centrifugal washing on it, and collect the final precipitate ZIF-67 to obtain 0.5 g of precipitate.

[0050] S3: Mix solution A and ZIF-67 and carry out ultrasonic stirring at a speed of 3000 r / min. After the stirring is completed, mix it with 0.75 g of polyvinylpyrrolidone and 3.86 g of N,N-dimethylformamide, and carry out magnetic stirring at 3000 r / min. After the stirring is completed, obtain a uniformly mixed precursor solution.

[0051] S4: Transfer the precursor solution into a 10 mL syringe equipped with a 21G spinneret. During the electrospinning process, the distance between the spinneret and the collection substrate is 15 cm, the spinning voltage is 20 kV, the feeding rate of the solution is 0.04 mL / min, and the collection is carried out using a drum collector with tin foil as the substrate.

[0052] S5: Place the collected fibers in a muffle furnace and heat them from room temperature to 150 °C at a heating rate of 2 °C / min, then heat them to 250 °C at a heating rate of 1 °C / min and hold for 3 h.

[0053] S6: Place the cured fibers in a tube furnace and heat them from room temperature to 250 °C at a heating rate of 2 °C / min, then heat them to 850 °C at a heating rate of 1 °C / min, and then heat them to 1300 °C at a heating rate of 2 °C / min, and hold for 5 h under a nitrogen atmosphere.

[0054] The fibers prepared by this method are fibers added with 0.5 g of ZIF-67 and with a pyrolysis temperature of 1300 °C.

[0055] The minimum reflection loss graph shown in Figure 1 (c) is obtained through vector network analysis testing.

[0056] By comparing Example 1 and Example 2, it is found that as the amount of ZIF-67 increases, the minimum reflection loss value of the fibers decreases, indicating that the addition of ZIF-67 improves the wave absorption performance of the fibers well.

[0057] By comparing Example 2 and Example 3, it is found that different high-temperature pyrolysis temperatures of the fibers will also cause changes in the performance of the wave-absorbing material.

[0058] Compared with traditional silicon carbide fibers, the present invention introduces ZIF-67 to complement its lacking magnetic properties and can regulate its absorption band and minimum reflection loss, etc. by the content of ZIF-67.

[0059] The present invention improves the original problem of insufficient flexibility of the ceramic material silicon carbide, and effectively improves the wave absorption performance of the material by doping ZIF-67. The prepared SiC-ZIF composite nanofibers have relatively good wave absorption performance when the thickness is 2.9 mm, and the minimum reflection loss can reach -52.65 dB; that is, due to the relatively high aspect ratio of the fiber itself, the interlaced porous network structure between the fibers, and the connection points between the interlaced fibers, the silicon carbide fiber material is endowed with good flexibility performance that it originally did not have, and at the same time, this structure also builds a good conductive network, thus improving the wave absorption performance.

[0060] The present invention improves the flexible mechanical properties of silicon carbide that ceramic materials do not have, so that it can be used in application scenarios such as wearable electronic devices, which has very practical application prospects in today's rapidly developing wireless communications environment.

[0061] The present invention increases the magnetic loss mechanism of silicon carbide fiber by introducing ZIF-67, and the introduction of metal not only improves the problem that the impedance matching of silicon carbide itself is difficult to control, but also forms a good conductive network with the structure staggered with the fiber itself, thereby improving the wave absorbing performance of the composite material.

[0062] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0063] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a silicon carbide flexible fiber material, characterized in that: The following steps are involved: Step S1: taking a first preset amount of polycarbosilane, grinding it into a powder in a mortar, and then dissolving it in chloroform, and the mixture is recorded as solution A; Step S2: taking a second preset amount of cobalt nitrate hexahydrate and 2-methylimidazole, respectively dissolving them in methanol and mixing them, and then subjecting the mixed solution to magnetic stirring, and after the stirring is completed, centrifuging and washing it to collect the final precipitate ZIF-67; Step S3: mixing solution A and precipitate ZIF-67 and subjecting them to ultrasonic stirring, and then mixing them with a third preset amount of polyvinyl pyrrolidone and N,N-dimethylformamide, and subjecting them to magnetic stirring, and obtaining a uniform precursor mixed solution after the stirring; Step S4: the precursor solution is transferred to a 10 mL syringe equipped with a 21G spinneret, and during the electrospinning process, a preset distance is set between the spinneret and the collecting substrate, a preset spinning voltage and a preset solution feed rate are set, and the solution is collected by a drum collector with tin foil as the substrate to obtain fibers; Step S5: placing the fiber in a muffle furnace and heating it at a first preset heating rate for a first preset number of times to raise the temperature to 200-300° C. and keep the temperature for 1-12 hours to solidify the fiber; Step S6, placing the cured fiber in a tubular furnace and heating it at a second preset heating rate for a second preset number of times to raise the temperature to 900-1300° C. and keeping it warm for 5-24 hours under a preset gas atmosphere; In step S1, the first preset amount of polycarbosilane is 0.5-1.5 g, and the chloroform is 10-20 mL; In step S2, the second preset amount of cobalt nitrate hexahydrate is 5-15 mL, 2-methylimidazole is 2-10 mL, methanol is 10-30 mL, the magnetic stirring time is 2-24 hours, and the magnetic stirring speed is 1500-3000 rpm; In step S3, the third preset amount of polyvinyl pyrrolidone is 0.5-1.5 g, the N,N-dimethylformamide is 2-5 g, the magnetic stirring speed is 1500-3000 rpm, and the stirring time is 2-24 hours; The silicon carbide flexible fiber material is a porous network structure.

2. The method for preparing a silicon carbide flexible fiber material according to claim 1, characterized in that: In step S3, the molecular weight of polyvinyl pyrrolidone is MW=130000 g / mol.

3. The method for preparing a silicon carbide flexible fiber material according to claim 1, characterized in that: In step S4, the preset distance between the spinneret and the collecting substrate is 15-25 cm, the preset spinning voltage is 10-25 kV, and the preset solution feed rate is 0.03-0.1 mL / min.

4. The method for preparing a silicon carbide flexible fiber material according to claim 1, characterized in that: In step S5, the first preset heating rate is 1-5°C / min, the first heating temperature is 150-200°C, and the second heating temperature is 200-300°C.

5. The method for preparing a silicon carbide flexible fiber material according to claim 1, characterized in that: In step S6, the second heating rate is 1-5°C / min, the first heating temperature is 200-300°C, the second heating temperature is 600-900°C, the third heating temperature is 900-1300°C, and the insulation temperature is 900-1300°C.

6. A silicon carbide flexible fiber material prepared by the preparation method according to any one of claims 1 to 5; characterized in that: The silicon carbide flexible fiber material is a porous network structure.

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