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A kind of silicon nitride nanofiber reinforced boron nitride ceramics and preparation method thereof

A nanofiber and silicon nitride technology, which is applied in the field of special functional ceramics, can solve the problems of complex deposition system of boron nitride ceramic matrix and adverse effects of wave transmission performance.

Active Publication Date: 2020-10-30
NAT INNOVATION INST OF DEFENSE TECH PLA ACAD OF MILITARY SCI
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Problems solved by technology

[0005] CN201310178854.4 discloses a method for preparing wave-transparent fiber-toughened boron nitride ceramic-based wave-transparent composite material by chemical vapor infiltration. The wave-transparent fiber fabric is used as the prefabricated body, and BCl 3 -NH 3 -Ar-H 2 Pioneer gas system, BN substrate prepared by chemical vapor infiltration process, this method can reduce the damage to the fiber, but the deposition system of the prepared boron nitride ceramic substrate is relatively complicated, and the impurities need to be strictly controlled to avoid damage to the permeation. adverse effect on wave performance

Method used

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  • A kind of silicon nitride nanofiber reinforced boron nitride ceramics and preparation method thereof
  • A kind of silicon nitride nanofiber reinforced boron nitride ceramics and preparation method thereof
  • A kind of silicon nitride nanofiber reinforced boron nitride ceramics and preparation method thereof

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preparation example Construction

[0034] The invention also provides a preparation method of silicon nitride nanofiber reinforced boron nitride wave-transparent ceramics, figure 1 It is a process flow diagram of the inventive method, comprising the following steps:

[0035] Step 1. Dispersion of silicon nitride nanofibers in liquid borazine, heating up to 150-250°C, under a protective atmosphere with oxygen content and water content <1ppm, silicon nitride with a mass percentage of 1-6wt.% The nanofibers are added to the liquid borazine, and the nanofibers are dispersed by magnetic stirring to obtain a mixed solution; the magnetic stirring speed is 300-400 rpm, that is, 300-400 revolutions per minute.

[0036] Step 2. Solidification of the mixed solution: transfer the mixed solution to an autoclave, fill it with 5-8MPa nitrogen as a protective gas, heat the mixed solution to 150-250°C at a heating rate of 5-10°C / min and keep it warm for 3- For 5 hours, the solution was solidified to obtain a solidified produc...

Embodiment 1

[0041] figure 2 It is the macroscopic topography diagram of the bulk ceramics prepared by the method of the present invention. refer to figure 1 In the glove box, adjust and keep the oxygen content and water content in the atmosphere < 1ppm, the silicon nitride nanofibers with a mass percentage of 1.2wt.% are gradually added to the liquid borazine, and stirred by magnetic force Disperse the nanowires, the magnetic stirring speed is 300rpm, and the stirring time is 4h to obtain a mixed solution;

[0042] (2) Transfer the mixed solution to an autoclave, fill it with 5MPa nitrogen as a protective gas, and while maintaining the magnetic stirring speed at 300rpm, heat the mixed solution to 200°C at a heating rate of 5°C / min and keep it warm for 3h, so that The mixed solution solidified;

[0043] (3) The cured product of the mixed solution is pulverized by a pulverizer to obtain a mixed powder of the nanofiber and borazine cured product, and the microscopic appearance of the mix...

Embodiment 2

[0047] (1) In the glove box, keep the oxygen content and water content in the atmosphere <1ppm, gradually add silicon nitride nanofibers with a mass percentage of 5.5wt.% to liquid borazine, and stir the nanowires by magnetic force Disperse, the magnetic stirring speed is 300rpm, and the stirring time is 4h to obtain a mixed solution;

[0048] (2) Transfer the mixed solution to an autoclave, fill it with 8MPa nitrogen as a protective gas, and while maintaining the magnetic stirring speed at 400rpm, heat the mixed solution to 250°C at a heating rate of 10°C / min and keep it warm for 5h, so that The solution solidifies;

[0049] (3) Grinding the cured product of the mixed solution with a pulverizer to obtain a mixed powder of the nanofiber and borazine cured product;

[0050] (4) Place the mixed powder obtained in step (3) in a hot-press sintering furnace, apply a hot-press pressure of 15 MPa under the condition of nitrogen protection, and raise the temperature to 1600°C at a he...

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Abstract

The invention provides a silicon nitride nanometer fiber reinforced boron nitride wave-transmitting ceramic, and a preparation method thereof. The silicon nitride nanometer fiber reinforced boron nitride wave-transmitting ceramic comprises silicon nitride nanometer fiber, and boron nitride ceramic; the silicon nitride nanometer fiber is uniformly dispersed in the boron nitride ceramic; the mass amount of the silicon nitride nanometer fiber ranges from 1 to 6wt%, the ceramic density ranges from 1.80 to 2.02g / cm3, the compactness ranges from 95.3 to 97.2%, the bending strength ranges from 75.2 to 107.8MPa, and the flexural modulus ranges from 28.1 to 36.3GPa. The preparation method comprises following steps: 1, silicon nitride nanometer fiber is subjected to stirring dispersion in liquid state borazine so as to form a mixed solution; 2, the mixed solution is heated to 150 to 250 DEG C for curing so as to obtain a cured product; 3, the cured product is crushed so as to obtain a mixed powder; and 4, the mixed powder is subjected to hot pressing sintering at 1200 to 1700 DEG C. The technology is controllable; operation is simple; ceramic performance is easy to adjust; the prepared product possesses excellent mechanical, thermal, and dielectric comprehensive performance, and is promising in application prospect in the fields of high temperature crucible, spaceflight wave-transmitting, and heat protection materials.

Description

technical field [0001] The invention belongs to the technical field of special functional ceramics, and in particular relates to enhanced boron nitride wave-transmitting ceramics and a preparation method thereof. Background technique [0002] Hexagonal boron nitride ceramics have excellent high temperature resistance, thermal shock resistance, ablation resistance, molten metal erosion resistance, neutron absorption performance, dielectric wave transmission performance and mechanical processability, and can be arranged through the orientation of grains Realizing the anisotropic adjustment of thermoelectric properties has important application prospects in aerospace, special smelting, high temperature wave-transparent radome / window and other fields. [0003] As a single-phase ceramic, boron nitride is a typical covalent bond compound, and its sintering performance is poor. Usually, it is necessary to actively add sintering aids and sinter at high temperature to make it densifi...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C04B35/80C04B35/583C04B35/622C04B35/645
CPCC04B35/583C04B35/622C04B35/645C04B2235/524C04B2235/77
Inventor 邹春荣沈同圣郭少军周晓松汪涛黎松
Owner NAT INNOVATION INST OF DEFENSE TECH PLA ACAD OF MILITARY SCI
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