Fiber-like nanofiber wave-absorbing material and preparation method thereof

Abstract

The fiber-like nanofiber wave-absorbing material provided by the invention comprises the ZrC / C fiber and the ZrO2 oxide layer coated on the surface of the ZrC / C fiber, overcomes the defects of the conventional wave-absorbing material, and has a wide application prospect. The invention also provides a preparation method of the fiber-like nanofiber wave-absorbing material, the ZrO2 crystal grain oxide layer is prepared on the surface of the ZrC / C fiber on the basis of keeping the fiber structure by combining an in-situ oxidation method with electrostatic spinning, and the method is simple, easy to operate and convenient for expanded production.

Description

Technical Field

[0001] The invention relates to a wave absorbing material, in particular to an optical fiber-like nanofiber wave absorbing material and a preparation method thereof. Background Art

[0002] With the application of digital information technology, modern electronic information technology has developed rapidly, and the interconnection of all things has become the norm. Information interconnection brings convenience, but the electromagnetic radiation generated by electronic devices is spread all over the world. Excessive electromagnetic radiation can interfere with precision instruments and affect signal transmission. In the military field, with the advancement of radar detection and weapon guidance technology, weapons and equipment are easily detected, tracked and attacked by the enemy. Electromagnetic wave absorbing materials can effectively solve electromagnetic radiation pollution, be used for military counter-reconnaissance, and improve the concealment of weapons and equipment. Therefore, absorbing materials with the characteristics of "wide, thin, strong and light" have a huge demand gap for high-tech and extreme environment applications.

[0003] At present, the commonly used absorbing materials mainly include conductive polymers, ferrites, carbon composites, three-dimensional inhomogeneous structural materials, etc. However, due to their own characteristics, most absorbing materials are difficult to use in high-temperature and harsh environments. For example, the performance of traditional electromagnetic shielding materials such as ferrites is seriously degraded at the Curie temperature, and conductive polymers and carbon composites have poor thermal stability and are easily oxidized. In addition, the high density of traditional absorbing materials and the reliance of three-dimensional structural materials on spatial structures will limit the application of materials to a certain extent.

[0004] In order to solve the above problems, people have been seeking an ideal technical solution. Summary of the invention

[0005] The purpose of the present invention is to provide an optical fiber-like nanofiber absorbing material and a preparation method thereof in view of the deficiencies in the prior art.

[0006] Specifically, ZrC ceramics in transition metal carbides (TMC) are typical ultra-high temperature ceramics. Their high melting point, oxidation resistance, high temperature stability and other characteristics are widely used in the hot end of aircraft. From another perspective, its high electrical conductivity also makes it a potential high-temperature absorbing material. Therefore, ZrC / C fibers prepared with ZrC can have a mesh conductive structure while having the high temperature stability and oxidation resistance of ZrC. However, the high conductivity of ZrC itself also causes a serious mismatch in the fiber surface impedance, resulting in strong reflection of electromagnetic waves.

[0007] The present invention provides a method for preparing ZrO by in-situ oxidation on the surface of ZrC / C fiber. 2 The grain layer is used to reduce the fiber conductivity, thereby improving surface impedance matching, enhancing interface polarization, and improving the fiber's electromagnetic wave absorption performance.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows: A kind of fiber-like nanofiber microwave absorbing material, comprising ZrC / C fibers and a ZrO 2 oxide layer coated on the surface of the ZrC / C fibers.

[0009] The ZrC / C fibers are interconnected to form a spatial network structure, and the ZrO 2 is circular or elliptical grains grown on the fiber surface.

[0010] A preparation method of the above-mentioned fiber-like nanofiber microwave absorbing material, which comprises the following steps: S1: Prepare a spinning solution containing zirconium element and carbon element; the molar ratio of zirconium element to carbon element is 1:(3-7); S2: Electrospinning to obtain a precursor fiber membrane; S3: The precursor fiber membrane is dried, cured and carbonized to obtain ZrC / C fibers; S4: The ZrC / C fibers are oxidized to obtain ZrO 2 The ZrC / C fiber material uniformly coated with an oxide layer.

[0011] Curing is carried out at 200-350 °C for 1-2 h; under an argon atmosphere, carbonization is carried out at 1500-1600 °C for 1-3 h, and the curing and carbonization processes are carried out under an argon atmosphere.

[0012] In step S4, oxidation is carried out by heating at 500-700 °C for 3-5 min under an air atmosphere.

[0013] The spinning solution includes a carbon source and a zirconium source; the carbon source includes a carbon-containing organic matter, a polymer and an organic solvent with a mass ratio of (8-10):10:(70-100); the zirconium source includes a zirconium organic salt, absolute ethanol and a stabilizer with a volume ratio of 4:(2-5):1.

[0014] The carbon-containing organic matter is glucose, sucrose or cellulose; the polymer is polystyrene, polyvinyl alcohol or polyvinylpyrrolidone; the organic solvent is absolute ethanol or N,N-dimethylformamide.

[0015] The zirconium-containing organic salt is zirconium n-propoxide or zirconium acetylacetonate; the stabilizer is acetylacetone, acetic acid or acetone.

[0016] In step S2, the electrospinning conditions are: temperature: 20-25 °C, humidity: 40-60%, distance between the roller and the spinning solution: 10-15 cm, spinning rate: 0.01-0.1 mL / min, spinning voltage: +8.0-+11.0 KV, -1.0 - -0.5 KV.

[0017] In step S3, the precursor fiber membrane is vacuum dried at 50-80 °C for 10-16 h, and then solidified.

[0018] The present invention has prominent substantive features and significant progress compared with the prior art. Specifically, the present invention provides a fiber-like nano-fiber absorbing material, including ZrC / C fibers and a ZrO 2 oxide layer coated on the surface of the ZrC / C fibers. The ZrC / C fibers are interconnected to form a spatial network structure, which significantly improves the conductivity of the composite material; in addition, the ZrO 2 grains grown on the surface of the ZrC / C fibers introduce ZrC / ZrO 2 , ZrO 2 / C and other interface layers. The existence of a large number of interfaces enables the material to generate more polarization phenomena under the action of an electromagnetic field, which can adjust the electromagnetic parameters of the ZrC fibers, thereby optimizing the impedance matching between the fibers and free space, and further increasing the interfacial polarization loss; furthermore, the ZrO 2 grains can also guide more electromagnetic waves into the interior of the fibers to be absorbed, rather than being reflected by the fiber surface; multiple mechanisms such as interfacial polarization, conductance loss, and scattering act synergistically to enhance the attenuation ability of the fibers to electromagnetic waves. At the same time, the present invention also provides a preparation method for the fiber-like nano-fiber absorbing material. By using the in-situ oxidation method combined with electrospinning, a ZrO 2 grain oxide layer is prepared on the surface of the ZrC / C fibers while retaining the fiber structure. This method is simple, easy to operate, and convenient for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the SEM image of the precursor ZrC fibers in Example 1 of the present invention; Figure 2 It is the SEM image of the ZrC / C fibers after carbonization in Example 1 of the present invention; Figure 3 It is the low-magnification SEM image of the fiber-like nano-fiber absorbing material in Example 1 of the present invention; Figure 4 It is the high-magnification SEM image of the fiber-like nano-fiber absorbing material in Example 1 of the present invention; Figure 5 It is the XRD pattern of the fiber-like nano-fiber absorbing material in Example 1 of the present invention; Figure 6 It is the electromagnetic wave reflection loss diagram of the fiber-like nano-fiber absorbing material in Example 1 of the present invention in the 2-18 GHz band DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The technical solution of the present invention is further described in detail below through specific implementation methods. It should be noted that the various devices involved in the following embodiments are all commercially available devices in the prior art, and similar devices can be used as needed. Example

[0021] This embodiment provides a fiber-like nanofiber absorbing material, including ZrC / C fiber and ZrO coated on the surface of the ZrC / C fiber. 2 Oxide layer; ZrC / C fibers are interconnected to form a spatial network structure, ZrO 2 These are round or elliptical grains that grow on the fiber surface.

[0022] This type of optical fiber nanofiber absorbing material can be prepared by the following steps: 1. Take carbon-containing organic matter, high molecular polymer and organic solvent in a mass ratio of (8-10):10:(70-100), heat and stir to dissolve at 70-90°C to obtain a carbon source; 2. Mix the zirconium-containing organic salt, anhydrous ethanol and stabilizer in a volume ratio of 4: (2-5): 1, and stir at room temperature for 2 hours, in order to polymerize the zirconium-containing organic salt to obtain a stable polymer, which is a zirconium source; 3. Mix the carbon source and the zirconium source and stir them at room temperature overnight to make the two mixed evenly to obtain a spinning solution; 4. The temperature and humidity are controlled between 20 and 25°C and 40 and 60, respectively, the roller is 10 to 15 cm away from the spinning solution, and electrospinning is performed at a propulsion speed of 0.01 to 0.1 mL / min under the conditions of +8.0 KV to +11.0 KV and -1.0 KV to -0.5 KV to obtain a precursor fiber membrane; 5. Place the precursor fiber membrane in a vacuum drying oven at 50-80°C to remove residual anhydrous ethanol until it is completely dry; 6. Spread the dried precursor fiber film flat in a carbon crucible, press the fiber film flat with a carbon plate, then place the carbon crucible in a tubular furnace, continuously introduce 0.16 mL / min argon gas flow for protection, heat up to 200-350°C at a certain rate, keep warm for 1-2 h, solidify the fiber to obtain solidified fiber. Then heat up to 1500-1600°C at a certain rate, keep warm for 1-3 h, and take out to obtain ZrC / C fiber.

[0023] 7. Place the ZrC / C fiber in a muffle furnace, control the oxidation temperature between 500 and 700 °C, and take it out after oxidation for 3 to 5 minutes to obtain ZrO 2 Layer-coated ZrC / C fiber, that is, optical fiber-like nanofiber absorbing material.

[0024] Example 1 This embodiment provides a fiber-like nanofiber absorbing material, which includes ZrC / C fibers and a ZrO oxide layer coated on the surface of the ZrC / C fibers. 2 For its XRD pattern, see Figure 5 ; see the appendix Figure 3-4 , where the ZrC / C fibers are interconnected to form a spatial network structure, and the ZrO 2 are circular or oval grains grown on the fiber surface. Through electromagnetic parameter testing with a vector network analyzer, the minimum reflection loss value of the fiber-like nanofiber absorbing material calculated from the measured dielectric constant is: -53.72 dB, and the maximum effective absorption bandwidth is 4.02 GHz.

[0025] This embodiment also provides a preparation method for the fiber-like nanofiber absorbing material, which includes the following steps: Take 0.86 g of sucrose and add it to a solution prepared from 0.83 g of polyvinylpyrrolidone and 6.4 ml of DMF, and heat and dissolve it at 80 °C for about 2 h to obtain a carbon source; take zirconium propoxide: absolute ethanol: acetylacetone = 1.6 ml: 1.2 ml: 0.4 ml, and obtain a zirconium source after stirring at room temperature for 2 h. Mix the carbon source and the zirconium source, stir overnight at room temperature to obtain an electrospinning solution; perform electrospinning on the electrospinning solution under the conditions of a voltage of +10 KV, -1.0 KV, a spinning distance of 15 cm, a spinning inner diameter of 0.52 mm, and a spinning speed of 0.01 mL / min to obtain a precursor fiber membrane. Dry the precursor fiber membrane in a vacuum at 60 °C for 12 h to ensure complete removal of anhydrous ethanol as a solvent; lay the dried precursor fiber membrane flat in a carbon crucible, press the fiber membrane flat with a carbon plate, then place the carbon crucible in a tube furnace, continuously introduce an argon gas flow of 0.16 mL / min for protection, heat up to 350 °C, keep it warm for 90 min to cure the fibers; then heat up to 1500 °C, take it out after keeping it warm for 90 min to obtain ZrC / C fibers.

[0026] Place the ZrC / C fibers in a carbon crucible, place the crucible in a muffle furnace, and oxidize it at 550 °C for 5 min to obtain the above-mentioned fiber-like nanofiber absorbing material.

[0027] Example 2 This embodiment provides a fiber-like nanofiber absorbing material, which includes ZrC / C fibers and a ZrO oxide layer coated on the surface of the ZrC / C fibers; the ZrC / C fibers are interconnected to form a spatial network structure, and the ZrO 2 are circular or oval grains grown on the fiber surface. 2

[0028] This type of fiber-optic nanofiber microwave absorbing material can be prepared through the following steps: Take 0.85 g of glucose and add it to a solution prepared from 0.9 g of polyacrylonitrile and 8.58 ml of DMF, and heat and dissolve at 80 °C for about 2 h to obtain a carbon source; take zirconium propoxide: absolute ethanol: acetylacetone = 1.6 ml: 1.2 ml: 0.4 ml, and obtain a zirconium source after stirring at room temperature for 2 h; Mix the carbon source and the zirconium source, stir overnight at room temperature to obtain an electrospinning solution; perform electrospinning on the electrospinning solution under the voltage conditions of +11.5 KV and -0.8 KV, a spinning distance of 15 cm, a spinning inner diameter of 0.52 mm, and a spinning speed of 0.01 ml / min to obtain a precursor fiber membrane; Vacuum-dry the precursor fiber membrane at 60 °C for 12 h to ensure complete removal of the solvent absolute ethanol; lay the dried precursor fiber membrane flat in a carbon crucible, flat-press the fiber membrane with a carbon plate, then place the carbon crucible in a tube furnace, continuously introduce an argon gas flow of 0.16 mL / min for protection, heat up to 300 °C, keep warm for 90 min to solidify the fiber; heat up to 1500 °C, take out after keeping warm for 90 min to obtain ZrC / C fibers.

[0029] Place the ZrC / C fibers in a carbon crucible, place the crucible in a muffle furnace, and oxidize at 600 °C for 4 min to obtain a fiber-optic nanofiber microwave absorbing material.

[0030] Example 3 This example provides a fiber-optic nanofiber microwave absorbing material, including ZrC / C fibers and a ZrO 2 oxide layer; the ZrC / C fibers are interconnected to form a spatial network structure, and ZrO 2 are circular or elliptical grains grown on the fiber surface.

[0031] Take 0.87 g of cellulose and add it to a solution prepared from 0.88 polyvinylpyrrolidone and 6.5 ml of DMF, and heat and dissolve at 80 °C for about 2 h to obtain a carbon source; take zirconium propoxide: absolute ethanol: acetic acid = 1.6 ml: 1.2 ml: 0.4 ml, stir at room temperature for 2 h to obtain a zirconium source; Mix the carbon source and the zirconium source, stir overnight at room temperature to obtain an electrospinning solution. Perform electrospinning on the electrospinning solution under the voltage conditions of +12.3 KV and -0.8 KV, a spinning distance of 15 cm, a spinning inner diameter of 0.61 mm, and a spinning speed of 0.015 ml / min to obtain a precursor fiber membrane; The precursor fiber membrane was dried in vacuum at 60 °C for 12 h to ensure complete removal of the solvent absolute ethanol; the dried precursor fiber membrane was laid flat in a carbon crucible, and the fiber membrane was flat-pressed with a carbon plate. Subsequently, the carbon crucible was placed in a tube furnace, and an argon gas flow of 0.16 mL / min was continuously introduced for protection. The temperature was raised to 350 °C and held for 90 min to cure the fibers; the temperature was raised to 1500 °C, and after holding for 90 min, it was taken out to obtain ZrC / C fibers; The ZrC / C fibers were placed in a carbon crucible, and the crucible was placed in a muffle furnace and oxidized at 700 °C for 3 min to obtain a fiber-optic-like nanofiber microwave absorption material.

[0032] Appearance description The precursor fiber membranes obtained in Examples 1 to 3 were all slightly yellowish white and had good flexibility; after carbonization, they were black fiber membranes and had a certain degree of flexibility. After oxidation treatment, the appearance of Example 1 was black and flexible, the appearance of Example 2 was grayish black and had a certain degree of flexibility, and Example 3 was white-gray.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: modifications can still be made to the specific implementation manners of the present invention or equivalent replacements can be made to some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. An optical fiber-like nanofiber absorbing material, characterized in that: It includes ZrC / C fiber and a ZrO2 oxide layer coated on the surface of the ZrC / C fiber.

2. The optical fiber-like nanofiber absorbing material according to claim 1, characterized in that: The ZrC / C fibers are interconnected to form a spatial network structure, and ZrO2 is round or elliptical grains growing on the fiber surface.

3. A method for preparing the optical fiber-like nanofiber absorbing material according to claim 1 or 2, comprising the following steps: S1: preparing a spinning solution containing zirconium and carbon; the molar ratio of zirconium to carbon is 1:(3-7); S2: Electrospinning to obtain precursor fiber membrane; S3: The precursor fiber membrane is dried, cured, and carbonized to obtain ZrC / C fiber; S4: The ZrC / C fiber is subjected to oxidation treatment to obtain a ZrC / C fiber material uniformly coated with a ZrO2 oxide layer.

4. The preparation method according to claim 3, characterized in that: In step S3, the temperature is kept at 200-350° C. for 1-2 h for curing; and the temperature is kept at 1500-1600° C. for 1-3 h for carbonization under an argon atmosphere. The curing and carbonization processes are carried out under an argon atmosphere.

5. The preparation method according to claim 4, characterized in that: In step S4, oxidation is performed by heating at 500 to 700° C. for 3 to 5 minutes in an air atmosphere.

6. The preparation method according to claim 5, characterized in that: The spinning solution includes a carbon source and a zirconium source; the carbon source includes carbon-containing organic matter, high molecular polymer and organic solvent in a mass ratio of (8-10):10:(70-100); the zirconium source includes zirconium organic salt, anhydrous ethanol and a stabilizer in a volume ratio of 4:(2-5):

1.

7. The preparation method according to claim 6, characterized in that: The carbon-containing organic matter is glucose, sucrose or cellulose; the high molecular polymer is polystyrene, polyvinyl alcohol or polyvinyl pyrrolidone; and the organic solvent is anhydrous ethanol or N,N-dimethylformamide.

8. The preparation method according to claim 7, characterized in that: The zirconium-containing organic salt is zirconium n-propoxide or zirconium acetylacetonate; the stabilizer is acetylacetone, acetic acid or acetone.

9. The preparation method according to claim 8, characterized in that: In step S2, the electrospinning conditions are: temperature: 20-25°C, humidity: 40-60%, distance between roller and spinning solution: 10-15 cm, spinning rate: 0.01-0.1 mL / min, spinning voltage: +8.0-+11.0 KV, -1.0--0.5 KV.

10. The preparation method according to claim 9, characterized in that: In step S3, the precursor fiber membrane is vacuum dried at 50-80° C. for 10-16 h, and then cured.

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