A kind of preparation method of boron modified silicon nitride fiber

A technology of silicon nitride fiber and boron modification, which is applied in the direction of inorganic raw material artificial filaments, can solve the problems of adverse effects on the spinnability of the precursor, damage to the fibril structure, and low content of B elements, so as to improve the mechanical properties, Improved stability and high activity

Inactive Publication Date: 2016-09-07
NAT UNIV OF DEFENSE TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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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 modified silicon nitride fiber
  • A kind of preparation method of boron modified silicon nitride fiber

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Experimental program
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Embodiment 1

[0040] (1) Preparation of highly active Si-N fibers. Put polycarbosilane non-melting fibers in the decarburization-nitriding system, vacuumize, then replace the gas in the system with nitrogen to normal pressure, repeat at least three times; feed high-purity ammonia gas, and heat up, heating system: 2 hours Raise the temperature to 500°C, raise the temperature to 700°C at 0.8°C / min, keep it for 0.5h, raise the temperature to 1200°C at 100°C / h, and keep it for 1h. Cool to room temperature with nitrogen gas to obtain highly active Si-N fibers; (2) Boronation of highly active Si-N fibers. In a nitrogen atmosphere, place highly active Si-N fibers and sodium fluoroborate in a decarburization-nitridation system, program the temperature up to 450°C, react for 24 hours, and cool to room temperature with nitrogen; (3) Nitrogen of boronized fibers change. Introduce high-purity ammonia gas, heat up to 1350°C for 6 hours, and keep warm for 1.5 hours. Cool to room temperature with nitro...

Embodiment 2

[0044] (1) Preparation of highly active Si-N fibers. Put polycarbosilane non-melting fibers in the decarburization-nitriding system, vacuumize, and then replace the gas in the system with argon to normal pressure, repeat at least three times; feed high-purity ammonia gas, and heat up, heating system: 2 The temperature was raised to 500°C in 1 hour, and then the temperature was raised to 700°C at 0.9°C / min, then kept for 0.5h, then raised to 1000°C at 100°C / h, and kept for 2h. Cool to room temperature with argon to obtain highly active Si-N fibers; (2) Boronation of highly active Si-N fibers. In an argon atmosphere, place the highly active Si-N fiber and potassium fluoroborate in a decarburization-nitridation system, program the temperature to 400°C, react for 30 hours, and cool to room temperature with argon; (3) boronized fiber Nitriding. Introduce high-purity ammonia gas, heat up to 1400°C for 6 hours, and keep warm for 1 hour. Cool to room temperature with argon, and it'...

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Abstract

The invention discloses a method for preparing boron-modified silicon nitride fiber. The method comprises the following steps: firstly, preparing high-activity Si-N fiber from polycarbosilane non-molten fiber in a conversion manner, performing chemical introduction of an element B through HF removal reaction between B-F compounds generated through pyrolysis of redundant N-H in the high-activity Si-N fiber and a borofluoride compound, and nitriding in an ammonia gas, thus preparing the boron-modified silicon nitride fiber. Compared with the prior art, the method disclosed by the invention has the advantage that the prepared boron-modified silicon nitride fiber is relatively high in boron content, relatively high in nitrogen content and relatively high in fiber strength. The method disclosed by the invention is simple and convenient in process, low in cost and applicable to large-scale production, and a conventional decarbonization-nitridation system does not need any transformation.

Description

technical field [0001] The invention relates to a method for preparing boron-modified silicon nitride fibers, in particular to a method for preparing boron-modified 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...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): D01F9/08C04B35/584C04B35/622
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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