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A kind of preparation method of boron-doped silicon nitride fiber

A silicon nitride fiber, boron-doped technology, applied in the direction of chemical characteristics of fibers, chemical post-processing of rayon, rayon of inorganic raw materials, etc., can solve the adverse effects of precursor spinnability, fibril structure damage, B element problems such as low content, to achieve the effect of improving mechanical properties, improving stability and high activity

Inactive Publication Date: 2017-02-22
NAT UNIV OF DEFENSE TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

After the B element is introduced into PCS, the B element content is generally low, and it has an adverse effect on the spinnability of the precursor
When the B element is introduced during the crosslinking process, due to the process of removing HCl, methyl, etc., it will cause great damage to the structure of the fibrils

Method used

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  • A kind of preparation method of boron-doped silicon nitride fiber
  • A kind of preparation method of boron-doped silicon nitride fiber

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Embodiment 1

[0040] (1) Preparation of highly active Si-N fibers. Put the polycarbosilane non-melting fiber in the decarburization-nitriding system, vacuumize, and then replace the gas in the system with nitrogen to normal pressure, repeat at least three times; feed high-purity ammonia gas, and raise the temperature at the same time, the heating system: 2 hours Raise the temperature to 500°C, raise the temperature to 600°C at 0.50°C / min, keep it warm for 0.5h, raise the temperature to 800-1200°C at 100°C / h, and keep it warm for 1h. Cool to room temperature with nitrogen gas to obtain highly active Si-N fibers; (2) Boronation of highly active Si-N fibers. After 2 hours, the temperature was raised to 200° C., and vaporized borazine was passed into the decarburization-nitridation system. The reaction time was 20 hours, and nitrogen gas was passed to cool to room temperature; (3) Nitriding of boronized fibers. Introduce high-purity ammonia gas, heat up to 1300°C for 6 hours, and keep warm for...

Embodiment 2

[0044] (1) Preparation of highly active Si-N fibers. Put polycarbosilane non-melting fibers in the decarburization-nitriding system, vacuumize, and replace the gas in the system with argon to normal pressure, repeat at least three times; feed high-purity ammonia gas, heating system: 2 hours to 500°C, 0.60°C / min to 600°C, heat preservation for 0.5h, 100°C / h to 1000°C, heat preservation for 1h. Cool to room temperature with argon to obtain highly active Si-N fibers; (2) Boronation of highly active Si-N fibers. After 2 hours, the temperature was raised to 250° C., and vaporized trichloroborazine was passed into the decarburization-nitridation system. The reaction time was 30 hours, and then cooled to room temperature by argon; (3) Nitriding of boronized fibers. Introduce high-purity ammonia gas, heat up to 1350°C for 6 hours, and keep warm for 1 hour. Cool to room temperature with argon, and it's done.

[0045] The X-photoelectron spectroscopy and radial B element X-ray photoe...

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Abstract

Disclosed is a preparation method of a boron-doped silicon nitride fiber. The preparation method comprises: preparing a high-activity Si-N fiber by adopting conversion of a dis-molten polycarbosilane fiber; realizing chemical introduction of the B element by utilizing HX elimination reaction between spare N-H in the high-activity Si-N fiber and borazine containing a B-X (X=H, Cl, Br, and I) bond; and performing nitridation in ammonia gas to prepare the boron-doped silicon nitride fiber. Compared with the prior art, the boron-doped silicon nitride fiber prepared through the method in the invention is relatively high in boron content, nitrogen content, and fiber strength, and is uniform in dispersion. According to the invention, the technology is simple; the cost is low; and no change is needed in a current decarburization-nitridation system, so that the preparation method is suitable for mass production.

Description

technical field [0001] The invention relates to a method for preparing boron-doped silicon nitride fibers, in particular to a method for preparing boron-doped silicon nitride fibers by transforming polycarbosilane fibers. Background technique [0002] Silicon nitride (Si 3 N 4 ) is one of the materials with the best comprehensive properties of structural ceramics, not only has excellent mechanical properties, high thermal stability, but also has a low dielectric constant. Its decomposition temperature is 1900°C, and its dielectric constant and dielectric loss are 7 and 4×10 respectively. -3 ~4.5×10 -3 , its ablation resistance is better than that of fused silica, and it can withstand thermal shock resistance under flight conditions of Mach 6-7. It is one of the ideal candidate materials for high-temperature wave-transparent ceramic fibers. [0003] The organic precursor conversion method is based on organic polymers (mostly organometallic polymers) as raw materials, and ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): D01F9/08D01F9/10D01F11/00C04B35/584C04B35/622
Inventor 谢征芳王军邵长伟宋永才王浩简科
Owner NAT UNIV OF DEFENSE TECH
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