Preparation method of wave-absorbing continuous SiCN ceramic fiber

A ceramic fiber and wave type technology, which is applied in the field of high-performance fiber preparation, can solve the problems of difficult introduction of electromagnetic waves, increased loss, and adverse effects on wave-absorbing performance, and achieve the effects of reduced reflection, reduced atomic ratio, and excellent wave-absorbing performance

Active Publication Date: 2019-06-18
NAT UNIV OF DEFENSE TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Therefore, purely high resistivity can only reduce reflection but not increase loss. Although purely low resistivity has large dielectric loss, it reflects electromagnetic waves and makes it difficult to introduce electromagnetic waves.
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  • Preparation method of wave-absorbing continuous SiCN ceramic fiber
  • Preparation method of wave-absorbing continuous SiCN ceramic fiber
  • Preparation method of wave-absorbing continuous SiCN ceramic fiber

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preparation example Construction

[0022] The present invention proposes a method for preparing a wave-absorbing continuous SiCN ceramic fiber, comprising the following steps:

[0023] S1: Place the polycarbosilane crosslinked fiber in a vacuum sintering furnace and vacuumize;

[0024] In the step S1, the C / Si atomic ratio of the polycarbosilane crosslinked fiber is 1.5-2, the weight retention rate in nitrogen at 1000°C is higher than 80%, and it will not melt and deform at 400°C; it has excellent wave-absorbing properties Ceramic fibers require a certain amount of SiC, Si 3 N 4 Different from C, etc., the selected polycarbosilane cross-linked fiber raw material can provide Si and C, polycarbosilane cross-linked fiber raw material can form SiC at high temperature, and then part of SiC becomes Si through atmosphere reaction 3 N 4 , the raw materials can meet the needs of use and are rich in sources and cheap in price.

[0025] The vacuuming is until the pressure in the vacuum sintering furnace is lower than ...

Embodiment 1

[0044] This embodiment provides a method for preparing a wave-absorbing continuous SiCN ceramic fiber, comprising the following steps:

[0045] S1: Put the polycarbosilane cross-linked fiber in a vacuum sintering furnace and evacuate to make the pressure in the furnace lower than 1Pa;

[0046] S2: Raise the temperature of the vacuum sintering furnace to 400°C, and then feed a mixture of ammonia and helium with a volume ratio of 1:1 at a flow rate of 1.5L / min until the pressure in the vacuum sintering furnace is 85kPa;

[0047] S3: Continue to feed the mixed gas of ammonia and helium at a flow rate of 1.5L / min, and at the same time raise the temperature in the vacuum sintering furnace from 400°C to 900°C at a heating rate of 1°C / min, and keep it in the vacuum sintering furnace The pressure remains unchanged at 85kPa, and stop feeding the mixed gas of ammonia and helium into the vacuum sintering furnace after the temperature reaches 900°C;

[0048] S4: Control the pressure in t...

Embodiment 2

[0057] This embodiment provides a method for preparing a wave-absorbing continuous SiCN ceramic fiber, comprising the following steps:

[0058] S1: Put the polycarbosilane cross-linked fiber in a vacuum sintering furnace and evacuate to make the pressure in the furnace lower than 1Pa;

[0059] S2: Raise the temperature of the vacuum sintering furnace to 400°C, and then feed a mixture of ammonia and helium with a volume ratio of 4:1 at a flow rate of 2.0L / min until the pressure in the vacuum sintering furnace is 95kPa;

[0060] S3: Continue to feed the mixed gas of ammonia and helium at a flow rate of 2.0L / min, and at the same time raise the temperature in the vacuum sintering furnace from 400°C to 900°C at a heating rate of 1.5°C / min, and keep the temperature in the vacuum sintering furnace The pressure remains unchanged at 95kPa, and stop feeding the mixed gas of ammonia and helium into the vacuum sintering furnace after the temperature reaches 900°C;

[0061] S4: Control th...

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Abstract

The invention discloses a preparation method of a wave-absorbing continuous SiCN ceramic fiber. The preparation method comprises S1, adding polycarbosilane crosslinked fibers in a vacuum sintering furnace, and vacuumizing; S2, heating the vacuum sintering furnace, and introducing a mixture of ammonia gas and helium gas; S3, introducing the mixture continuously, and keeping inner pressure of the vacuum sintering furnace unchanged; S4, heating the vacuum sintering furnace continuously, and stopping introducing the mixture into the vacuum sintering furnace; S5, reducing inner pressure of the vacuum sintering furnace, and continuing to heat the vacuum sintering furnace; S6, stopping heating the vacuum sintering furnace, and acquiring the wave-absorbing continuous SiCN ceramic fiber when the temperature of the vacuum sintering furnace drops to 50 DEG C and below. Compared with the prior art, the preparation method of the wave-absorbing continuous SiCN ceramic fiber has the advantages that the technical flow is simple; the prepared wave-absorbing continuous SiCN ceramic fiber has resistivity of 104-108 omega cm, lowest electromagnetic reflection loss of up to -63.7 dB and effective absorption bandwidth of 4.20 GHz; the wave-absorbing continuous SiCN ceramic fiber has high resistivity and excellent wave absorbing performance for X band and Ku band.

Description

technical field [0001] The invention relates to the technical field of high-performance fiber preparation, in particular to a preparation method of wave-absorbing continuous SiCN ceramic fiber. Background technique [0002] Microwave-absorbing ceramic fiber is the key raw material of high-temperature microwave-absorbing composite materials and an important material for realizing the stealth of high-temperature components. Due to the high C / Si atom ratio of polycarbosilane, the raw material of silicon carbide fiber, the SiC fiber made contains more free carbon, and the control of its composition structure is limited. It is easy to prepare ceramic fiber with low resistivity, but it is difficult to prepare ceramic fiber with resistivity higher than 10000Ω·cm absorbing ceramic fiber. [0003] To improve the wave-absorbing performance of the wave-absorbing fiber, on the one hand, it is necessary to reduce the reflection of electromagnetic waves, so that more electromagnetic wave...

Claims

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Application Information

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IPC IPC(8): C04B35/622
Inventor 邵长伟王军王浩简科
Owner NAT UNIV OF DEFENSE TECH
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