Preparation method of flexible SiBCNHf ceramic fiber fabric for high-temperature electromagnetic shielding

Abstract

The invention relates to a preparation method of a flexible SiBCNHf ceramic fiber fabric for high-temperature electromagnetic shielding, which comprises the following steps: (1) mixing a SiBCN precursor, a spinning aid, a curing agent, a hafnium-containing substance and a solvent, and uniformly stirring and mixing to obtain a spinning solution; (2) performing electrostatic spinning on the spinning solution to obtain a precursor, then performing cross-linking curing, and performing splitting decomposition in an inert atmosphere to obtain a flexible amorphous SiBCNHf ceramic fiber fabric; and (3) finally, carrying out high-temperature heat treatment. According to the invention, the SiBCNfHf ceramic fiber fabric with excellent flexibility is obtained by regulating and controlling the variety and content of an Hf source; in addition, controllable adjustment of electromagnetic parameters of the flexible SiBCNfHf ceramic fiber fabric is achieved by regulating and controlling the type and content of an Hf source and high-temperature heat treatment conditions, and then regulation and control of the high-temperature electromagnetic protection performance are achieved.

Description

Technical Field

[0001] The invention belongs to the field of inorganic non-metallic ceramic materials, and in particular relates to a method for preparing a flexible SiBCNHf ceramic fiber fabric for high-temperature electromagnetic shielding. Background Art

[0002] SiBCN ceramic fibers have the characteristics of low density, high temperature resistance, oxidation resistance and ablation resistance, and have great application potential in thermal structural parts of hypersonic aircraft. However, SiBCN ceramic fibers have two problems: first, due to the low electrical conductivity and dielectric constant, it is difficult to effectively attenuate electromagnetic waves; second, due to the strong covalent bonds and limited dislocation slip system, SiBCN ceramic fibers are still brittle. Therefore, further improvement of SiBCN ceramic fibers is needed. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing a flexible SiBCNHf ceramic fiber fabric for high-temperature electromagnetic shielding, which introduces a hafnium-containing substance and forms HfO in situ. 2 Nanocrystals greatly improve the flexibility of SiBCN ceramic fiber fabrics.

[0004] The present invention provides a method for preparing a flexible SiBCNHf ceramic fiber fabric for high-temperature electromagnetic shielding, comprising the following steps:

[0005] (1) mixing a SiBCN precursor, a spinning aid, a curing agent, a hafnium-containing substance and a solvent, and stirring and mixing them uniformly to obtain a precursor spinning solution;

[0006] (2) preparing raw fibers from the above-mentioned precursor spinning solution by electrospinning, and then cross-linking and curing them, and then cracking them under an inert atmosphere to obtain flexible amorphous SiBCNHf ceramic fiber fabrics;

[0007] (3) The amorphous SiBCNHf ceramic fiber fabric is subjected to high-temperature heat treatment to obtain a flexible SiBCNHf ceramic fiber fabric.

[0008] Preferably, the SiBCN precursor in step (1) is polyborosilazane containing vinyl functional groups, and has a molecular weight of 900 to 1000.

[0009] Preferably, the spinning aid in step (1) is at least one of polyacrylonitrile, polycaprolactone and polyvinyl pyrrolidone.

[0010] Preferably, the curing agent in step (1) is at least one of dicumyl peroxide or azobisisobutyronitrile.

[0011] Preferably, the hafnium-containing substance in step (1) is at least one of hafnium chloride, hafnium acetate or hafnium acetylacetonate.

[0012] Preferably, the solvent in step (1) is at least one of chloroform, N,N-dimethylformamide, toluene or xylene.

[0013] Preferably, the mass ratio of the SiBCN precursor, the spinning aid, the curing agent, the hafnium-containing substance and the solvent in the step (1) is 1:(0.1-1):(0.01-0.05):(0.1-1):(5-15).

[0014] Preferably, the stirring time in step (1) is 12 to 72 hours.

[0015] Preferably, the process parameters of the electrospinning in step (2) are: voltage of 10 to 30 V, flow rate of 0.2 to 3 mL / h, collection speed of 200 to 1000 rpm, moving speed of 0.2 to 1 mm / s, and round-trip distance of 30 to 130 mm.

[0016] Preferably, the cross-linking curing temperature in step (2) is 100 to 180° C. and the time is 1 to 5 hours.

[0017] Preferably, the process parameters of the cracking in step (2) are: the atmosphere is an inert atmosphere (Ar or N 2 ), the temperature is 600-1200°C, and the time is 1-3 hours. More preferably, the temperature is increased to 600-1200°C at 1-10°C / min and kept at this temperature for 1-3 hours.

[0018] Preferably, the process parameters of the high temperature heat treatment in step (3) are: the atmosphere is an inert atmosphere (Ar or N 2 ), the temperature is 1000-2000°C, and the time is 1-3 hours. More preferably, the temperature is increased to 1000-2000°C at 1-10°C / min, and kept at this temperature for 1-3 hours.

[0019] Beneficial Effects

[0020] (1) The present invention obtains SiBCNfHf ceramic fiber fabrics with excellent flexibility by regulating the type and content of Hf source; in addition, by regulating the type and content of Hf source and high-temperature heat treatment conditions, the electromagnetic parameters of the flexible SiBCNfHf ceramic fiber fabrics can be controlled, thereby achieving the regulation of high-temperature electromagnetic protection performance.

[0021] (2) The present invention uses polyborosilazane containing vinyl functional groups as a precursor and a free radical initiator as a curing agent, which can make the SiBCN precursor cross-linked and cured at a relatively low temperature, thereby avoiding the melting deformation of the precursor.

[0022] (3) The present invention introduces a suitable hafnium-containing substance and forms HfO in situ 2 Nanocrystals greatly improve the flexibility of SiBCN ceramic fiber fabrics.

[0023] (4) The preparation method of the present invention is applicable to different types of ceramic fiber fabrics and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 ab are optical photographs of the flexible SiBCNHf ceramic fiber fabric prepared in Example 1.

[0025] Figure 2 This is a scanning electron microscope image of the flexible SiBCNHf ceramic fiber fabric prepared in Example 1.

[0026] Figure 3 This is the X-ray diffraction pattern of the flexible SiBCNHf ceramic fiber fabric prepared in Example 1.

[0027] Figure 4 This is the overall shielding effectiveness diagram of the flexible SiBCNHf ceramic fiber fabric prepared in Example 1. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0029] Example 1

[0030] Polyborosilazane, polyacrylonitrile, diisopropylbenzene peroxide, hafnium chloride and N,N-dimethylformamide were weighed and mixed in a mass ratio of 1:0.6:0.02:0.5:10 and stirred for 12 hours to prepare a precursor spinning solution; a precursor fiber was prepared by electrospinning (spinning parameters: voltage of 10 V, flow rate of 0.2 mL / hr, collection speed of 200 rpm, moving speed of 0.2 mm / s, and round-trip distance of 100 mm); the precursor fiber was kept at 150°C for 2 hours (curing system: heating to 1 at 2°C / min) 50℃, keep warm for 2 hours); the solidified raw silk is cracked at 800℃, kept warm for 2 hours in an inert atmosphere (argon) (cracking system: heating to 800℃ at 5℃ / min, keeping warm for 2 hours) to obtain amorphous SiBCNHf ceramic fiber fabric; the amorphous SiBCNHf ceramic fiber fabric is heat treated at 1400℃, kept warm for 2 hours in an inert atmosphere (argon) (heat treatment system: heating to 1400℃ at 5℃ / min, keeping warm for 2 hours), and finally a flexible SiBCNHf ceramic fiber fabric is obtained. In this embodiment, the SiBCNHf ceramic fiber fabric exhibits excellent mechanical flexibility ( Figure 1 ); Scanning electron microscopy results show that the diameter of SiBCNHf fibers is less than 1μm ( Figure 2 ); X-ray diffraction results show that after heat treatment at 1400℃, HfO 2 Phase formation ( Figure 3 ); The total shielding effectiveness of SiBCNHf fiber fabric reaches 30dB at 10GHz ( Figure 4 ).

[0031] Example 2

[0032] Polyborosilazane, polycaprolactone, azobisisobutyronitrile, hafnium acetate and chloroform were weighed and mixed in a mass ratio of 1:0.5:0.01:1:15, and stirred for 48 hours to prepare a precursor spinning solution; a precursor fiber was prepared by electrospinning (spinning parameters: voltage of 20 V, flow rate of 1 mL / hr, collection speed of 800 rpm, moving speed of 1 mm / s, and round-trip distance of 100 mm); the precursor fiber was kept at 100°C for 2 hours (curing system: heating to 100°C at 2°C / min and kept at this temperature for 2 hours); the cured precursor fiber was The amorphous SiBCNHf ceramic fiber fabric was obtained by pyrolysis at 900°C and keeping warm for 2 hours under an inert atmosphere (argon) (pyrolysis system: heating to 900°C at 5°C / min and keeping warm for 2 hours). The amorphous SiBCNHf fiber fabric was heat treated at 1600°C and kept warm for 2 hours under an inert atmosphere (argon) (heat treatment system: heating to 1600°C at 5°C / min and keeping warm for 2 hours) to finally obtain a flexible SiBCNHf ceramic fiber fabric, which has similar mechanical flexibility to the ceramic fiber fabric obtained in Example 1.

[0033] Example 3

[0034] Polyborosilazane, polyvinyl pyrrolidone, azobisisobutyronitrile, hafnium acetylacetonate and chloroform were weighed and mixed in a mass ratio of 1:0.5:0.01:1:10, and stirred for 24 hours to prepare a precursor spinning solution; a precursor fiber was prepared by electrospinning (spinning parameters: voltage of 15 V, flow rate of 0.5 mL / hr, collection speed of 1000 rpm, moving speed of 0.5 mm / s, and round-trip distance of 100 mm); the precursor fiber was kept at 100°C for 2 hours (curing system: heating to 100°C at 2°C / min and keeping warm for 2 hours); the cured fiber was The raw silk was cracked at 1000°C and kept warm for 2 hours under an inert atmosphere (argon) (cracking system: heating to 1000°C at 5°C / min and keeping warm for 2 hours) to obtain amorphous SiBCNHf ceramic fiber fabric; the amorphous SiBCNHf ceramic fiber fabric was heat treated at 1800°C and kept warm for 2 hours under an inert atmosphere (argon) (heat treatment system: heating to 1800°C at 5°C / min and keeping warm for 2 hours) to finally obtain a flexible SiBCNHf ceramic fiber fabric, which has similar mechanical flexibility to the ceramic fiber fabric obtained in Example 1.

[0035] Example 4

[0036] Polyborosilazane, polyacrylonitrile, diisopropylbenzene peroxide, hafnium acetylacetonate and N,N-dimethylformamide were weighed and mixed in a mass ratio of 1:0.5:0.03:0.5:12, and stirred for 36 hours to prepare a precursor spinning solution; a precursor fiber was prepared by electrospinning (spinning parameters: voltage of 15 V, flow rate of 0.8 mL / hr, collection speed of 600 rpm, moving speed of 0.8 mm / s, and round-trip distance of 100 mm); the precursor fiber was kept at 180°C for 2 hours (curing system: heating to 180°C at 2°C / min and keeping warm for 2 hours); the solid The oxidized raw silk was cracked at 1000°C and kept warm for 3 hours under an inert atmosphere (argon) (cracking system: heating to 1000°C at 5°C / min and keeping warm for 3 hours) to obtain amorphous SiBCNHf ceramic fiber fabric; the amorphous SiBCNHf ceramic fiber fabric was heat treated at 1200°C and kept warm for 2 hours under an inert atmosphere (argon) (heat treatment system: heating to 1200°C at 10°C / min and keeping warm for 2 hours) to finally obtain a flexible SiBCNHf ceramic fiber fabric, which has similar mechanical flexibility to the ceramic fiber fabric obtained in Example 1.

[0037] Comparative Example 1

[0038] Polyborosilazane, polyvinyl pyrrolidone, dicumyl peroxide and chloroform were weighed and mixed in a mass ratio of 1:0.5:0.01:1:10, and stirred for 24 hours to prepare a precursor spinning solution; a precursor fiber was prepared by electrospinning (spinning parameters: voltage of 10 V, flow rate of 0.5 mL / hr, collection speed of 800 rpm, moving speed of 1 mm / s, and round-trip distance of 100 mm); the precursor fiber was kept at 150°C for 2 hours (curing system: heating to 150°C at 2°C / min, keeping warm for 2 hours) The solidified raw silk was pyrolyzed at 800°C and kept warm for 2 hours in an inert atmosphere (argon) (pyrolysis system: heating to 800°C at 5°C / min and keeping warm for 2 hours) to obtain an amorphous SiBCN ceramic fiber fabric; the amorphous SiBCN ceramic fiber fabric was heat treated at 1400°C and kept warm for 2 hours in an inert atmosphere (argon) (heat treatment system: heating to 1400°C at 5°C / min and keeping warm for 2 hours) to finally obtain a SiBCN ceramic fiber fabric, which has no mechanical flexibility.

Claims

1. A method for preparing a flexible SiBCNHf ceramic fiber fabric for high temperature electromagnetic shielding, comprising the following steps: (1) mixing a SiBCN precursor, a spinning aid, a curing agent, a hafnium-containing substance and a solvent, and stirring and mixing them uniformly to obtain a precursor spinning solution; (2) preparing raw fibers from the above-mentioned precursor spinning solution by electrospinning, and then cross-linking and curing them, and then cracking them under an inert atmosphere to obtain flexible amorphous SiBCNHf ceramic fiber fabrics; (3) The amorphous SiBCNHf ceramic fiber fabric is subjected to high-temperature heat treatment to obtain a flexible SiBCNHf ceramic fiber fabric.

2. The preparation method according to claim 1, characterized in that: The SiBCN precursor in step (1) is polyborosilazane containing vinyl functional groups, and has a molecular weight of 900 to 1000.

3. The preparation method according to claim 1, characterized in that: The spinning aid in step (1) is at least one of polyacrylonitrile, polycaprolactone and polyvinyl pyrrolidone.

4. The preparation method according to claim 1, characterized in that: The curing agent in step (1) is at least one of dicumyl peroxide and azobisisobutyronitrile.

5. The preparation method according to claim 1, characterized in that: The hafnium-containing substance in step (1) is at least one of hafnium chloride, hafnium acetate or hafnium acetylacetonate.

6. The preparation method according to claim 1, characterized in that: The solvent in step (1) is at least one of chloroform, N,N-dimethylformamide, toluene or xylene.

7. The preparation method according to claim 1, characterized in that: The mass ratio of the SiBCN precursor, the spinning aid, the curing agent, the hafnium-containing substance and the solvent in the step (1) is 1: (0.1-1): (0.01-0.05): (0.1-1): (5-15).

8. The preparation method according to claim 1, characterized in that: The process parameters of the electrospinning in step (2) are: voltage of 10-30 V, flow rate of 0.2-3 mL / h, collection speed of 200-1000 rpm, moving speed of 0.2-1 mm / s, and round-trip distance of 30-130 mm.

9. The preparation method according to claim 1, characterized in that: The temperature of the cross-linking curing in the step (2) is 100-180° C., and the time is 1-5 hours; the process parameters of the cracking are: the atmosphere is an inert atmosphere, the temperature is 600-1200° C., and the time is 1-3 hours.

10. The preparation method according to claim 1, characterized in that: The process parameters of the high temperature heat treatment in step (3) are: an inert atmosphere, a temperature of 1000 to 2000° C., and a time of 1 to 3 hours.

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