A method for preparing a flexible si-b-c-n-hf ceramic fiber fabric for high temperature electromagnetic shielding

Abstract

The application relates to a preparation method of a flexible SiBCNHf ceramic fiber fabric for high-temperature electromagnetic shielding, which comprises the following steps: (1) mixing SiBCN precursors, spinning assistants, curing agents, hafnium-containing substances and solvents, stirring and uniformly mixing to obtain a spinning solution; (2) preparing a raw yarn by utilizing electrostatic spinning on the spinning solution, then cross-linking and curing, and pyrolyzing under an inert atmosphere to obtain a flexible amorphous SiBCNHf ceramic fiber fabric; and (3) finally performing high-temperature heat treatment to obtain the SiBCNHf ceramic fiber fabric. The application can obtain the SiBCNfHf ceramic fiber fabric with excellent flexibility by regulating the type and content of the Hf source. In addition, the type and content of the Hf source and the high-temperature heat treatment conditions are regulated to realize controllable adjustment of electromagnetic parameters of the flexible SiBCNfHf ceramic fiber fabric, and then the high-temperature electromagnetic shielding performance is regulated.

Description

Technical Field

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

[0002] SiBCN ceramic fibers possess properties such as low density, high temperature resistance, oxidation resistance, and ablation resistance, making them highly promising for application in the thermal structural components of hypersonic aircraft. However, SiBCN ceramic fibers have two main drawbacks: firstly, their low electrical conductivity and dielectric constant make them difficult to effectively attenuate electromagnetic waves; secondly, the strong covalent bonds and finite dislocation slip system result in SiBCN ceramic fibers remaining brittle. Therefore, further improvements to SiBCN ceramic fibers are needed. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing flexible SiBCN ceramic fiber fabric for high-temperature electromagnetic shielding. This method significantly improves the flexibility of SiBCN ceramic fiber fabric by introducing hafnium-containing substances and forming HfO2 nanocrystals in situ.

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

[0005] (1) Mix the SiBCN precursor, spinning aid, curing agent, hafnium-containing substance and solvent, and stir until uniform to obtain the precursor spinning solution;

[0006] (2) The precursor spinning solution was electrospinned to obtain the original fiber, which was then crosslinked and cured, and then pyrolyzed under an inert atmosphere to obtain a flexible amorphous SiBCNHf ceramic fiber fabric.

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

[0008] Preferably, the SiBCN precursor in step (1) is a polyborosilicate containing vinyl functional groups with a molecular weight of 900-1000.

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

[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 SiBCN precursor, spinning aid, curing agent, hafnium-containing substance and solvent in 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 electrospinning process parameters in step (2) are: voltage of 10-30V, flow rate of 0.2-3mL / h, collection speed of 200-1000rpm, moving speed of 0.2-1mm / s, and round-trip distance of 30-130mm.

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

[0017] Preferably, the pyrolysis process parameters in step (2) are: an inert atmosphere (Ar or N2), a temperature of 600–1200°C, and a time of 1–3 h. More preferably, the temperature is increased to 600–1200°C at a rate of 1–10°C / min and held for 1–3 h.

[0018] Preferably, the process parameters for the high-temperature heat treatment in step (3) are: an inert atmosphere (Ar or N2), a temperature of 1000–2000°C, and a time of 1–3 h. More preferably, the temperature is increased to 1000–2000°C at a rate of 1–10°C / min and held for 1–3 h.

[0019] Beneficial effects

[0020] (1) This invention obtains SiBCNfHf ceramic fiber fabric with excellent flexibility by controlling the type and content of Hf source; in addition, the electromagnetic parameters of flexible SiBCNfHf ceramic fiber fabric can be controlled by controlling the type and content of Hf source and high temperature heat treatment conditions, thereby realizing the control of high temperature electromagnetic protection performance.

[0021] (2) The present invention uses polyborosilicate containing vinyl functional groups as a precursor and free radical initiator as a curing agent, which enables SiBCN precursor fibers to crosslink and cure at a lower temperature, avoiding melting deformation of the precursor fibers.

[0022] (3) By introducing a suitable hafnium-containing material and forming HfO2 nanocrystals in situ, the present invention significantly improves the flexibility of SiBCN ceramic fiber fabric.

[0023] (4) The preparation method of the present invention is applicable to different types of ceramic fiber fabrics and has good application prospects. Attached Figure Description

[0024] Figure 1 ab is an optical photograph of the flexible SiBCNHf ceramic fiber fabric prepared in Example 1.

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

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

[0027] Figure 4 The diagram shows the overall shielding effectiveness of the flexible SiBCNHf ceramic fiber fabric prepared in Example 1. Detailed Implementation

[0028] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0029] Example 1

[0030] Polyborosilazane, polyacrylonitrile, dicumyl 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 the precursor spinning solution. The precursor fiber was prepared by electrospinning (spinning parameters: voltage 10V, flow rate 0.2mL / hr, collection speed 200rpm, moving speed 0.2mm / s, round trip distance 100mm). The precursor fiber was then incubated at 150℃ for 2 hours (curing regime: temperature increased at 2℃ / min to 1...). The cured precursor fibers were then pyrolyzed at 800℃ and held at an inert atmosphere (argon) for 2 hours (pyrolysis regime: heating to 800℃ at 5℃ / min, holding for 2 hours) to obtain amorphous SiBCNHf ceramic fiber fabric. The amorphous SiBCNHf ceramic fiber fabric was then heat-treated at 1400℃ and held at an inert atmosphere (argon) for 2 hours (heat treatment regime: heating to 1400℃ at 5℃ / min, holding for 2 hours) to finally obtain flexible SiBCNHf ceramic fiber fabric. In this embodiment, the SiBCNHf ceramic fiber fabric exhibits excellent mechanical flexibility. Figure 1Scanning electron microscopy results show that the diameter of SiBCNHf fibers is less than 1 μm. Figure 2 X-ray diffraction results showed that after heat treatment at 1400℃, the HfO2 phase was formed. Figure 3 The overall shielding effectiveness of SiBCNHf fiber fabric reaches 30 dB at 10 GHz. Figure 4 ).

[0031] Example 2

[0032] Weigh out polyborosilazane, polycaprolactone, azobisisobutyronitrile, hafnium acetate, and chloroform in a mass ratio of 1:0.5:0.01:1:15, mix them, and stir for 48 hours to prepare the precursor spinning solution. Prepare the precursor fiber by electrospinning (spinning parameters: voltage 20V, flow rate 1mL / hr, collection speed 800rpm, moving speed 1mm / s, round-trip distance 100mm). Incubate the precursor fiber at 100℃ for 2 hours (curing regime: temperature increased to 100℃ at 2℃ / min, held for 2 hours). Then, in... The SiBCNHf ceramic fiber fabric was obtained by pyrolysis at 900℃ and holding at an inert atmosphere (argon) for 2 hours (pyrolysis regime: heating to 900℃ at 5℃ / min and holding for 2 hours). The amorphous SiBCNHf fiber fabric was then heat-treated at 1600℃ and held at an inert atmosphere (argon) for 2 hours (heat treatment regime: heating to 1600℃ at 5℃ / min and holding 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] Weigh out polyborosilazane, polyvinylpyrrolidone, azobisisobutyronitrile, hafnium acetylacetonate, and chloroform in a mass ratio of 1:0.5:0.01:1:10, mix them, and stir for 24 hours to prepare the precursor spinning solution. Prepare the precursor fiber by electrospinning (spinning parameters: voltage 15V, flow rate 0.5mL / hr, collection speed 1000rpm, moving speed 0.5mm / s, round trip distance 100mm). Incubate the precursor fiber at 100℃ for 2 hours (curing regime: temperature increased to 100℃ at 2℃ / min, held for 2 hours). After curing... The precursor fiber was pyrolyzed at 1000℃ and held at an inert atmosphere (argon) for 2 hours (pyrolysis regime: heating to 1000℃ at 5℃ / min, holding for 2 hours) to obtain amorphous SiBCNHf ceramic fiber fabric; the amorphous SiBCNHf ceramic fiber fabric was then heat-treated at 1800℃ and held at an inert atmosphere (argon) for 2 hours (heat treatment regime: heating to 1800℃ at 5℃ / min, holding for 2 hours) to finally obtain 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, dicumyl 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 the precursor spinning solution. The precursor fiber was prepared by electrospinning (spinning parameters: voltage 15V, flow rate 0.8mL / hr, collection speed 600rpm, moving speed 0.8mm / s, round trip distance 100mm). The precursor fiber was then incubated at 180℃ for 2 hours (curing regime: temperature increased to 180℃ at 2℃ / min, incubated for 2 hours). The pyrolysis of the precursor fiber was carried out at 1000℃ and held at an inert atmosphere (argon) for 3 hours (pyrolysis regime: heating to 1000℃ at 5℃ / min and holding for 3 hours) to obtain amorphous SiBCNHf ceramic fiber fabric. The amorphous SiBCNHf ceramic fiber fabric was then heat-treated at 1200℃ and held at an inert atmosphere (argon) for 2 hours (heat treatment regime: heating to 1200℃ at 10℃ / min and holding for 2 hours) to finally obtain flexible SiBCNHf ceramic fiber fabric, which has similar mechanical flexibility to the ceramic fiber fabric obtained in Example 1.

[0037] Comparative Example 1

[0038] Weigh out polyborosilazane, polyvinylpyrrolidone, dicumyl peroxide, and chloroform in a mass ratio of 1:0.5:0.01:1:10, mix them, and stir for 24 hours to prepare the precursor spinning solution. Prepare the precursor fiber by electrospinning (spinning parameters: voltage 10V, flow rate 0.5mL / hr, collection speed 800rpm, moving speed 1mm / s, round trip distance 100mm). Incubate the precursor fiber at 150℃ for 2 hours (curing regime: temperature increased to 150℃ at 2℃ / min, held for 2 hours). The cured filaments were then pyrolyzed at 800℃ and held in an inert atmosphere (argon) for 2 hours (pyrolysis regime: heating to 800℃ at 5℃ / min, holding for 2 hours) to obtain amorphous SiBCN ceramic fiber fabric. The amorphous SiBCN ceramic fiber fabric was then heat-treated at 1400℃ and held in an inert atmosphere (argon) for 2 hours (heat treatment regime: heating to 1400℃ at 5℃ / min, holding for 2 hours) to finally obtain SiBCN ceramic fiber fabric, which does not possess mechanical flexibility.

Claims

1. A method for preparing a flexible SiBCNHf ceramic fiber fabric for high-temperature electromagnetic shielding, comprising the following steps: (1) The SiBCN precursor, spinning aid, curing agent, hafnium-containing substance, and solvent are mixed and stirred until homogeneous to obtain the precursor spinning solution; wherein, The SiBCN precursor is a polyborosilicate containing vinyl functional groups with a molecular weight of 900-1000; the curing agent is at least one of dicumyl peroxide or azobisisobutyronitrile. (2) The precursor spinning solution is used to prepare the original fiber by electrospinning, then crosslinked and cured, and then pyrolyzed under an inert atmosphere to obtain a flexible amorphous SiBCNHf ceramic fiber fabric; wherein the crosslinking and curing temperature is 100-150℃ and the time is 1-5h. (3) The above-mentioned amorphous SiBCNHf ceramic fiber fabric is subjected to high-temperature heat treatment to obtain flexible SiBCNHf ceramic fiber fabric.

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

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

4. 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.

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

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

7. The preparation method according to claim 1, characterized in that: The pyrolysis process parameters in step (2) are: inert atmosphere, temperature 600-1200℃, and time 1-3h.

8. The preparation method according to claim 1, characterized in that: The process parameters for the high-temperature heat treatment in step (3) are: inert atmosphere, temperature 1000~2000℃, and time 1~3h.

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