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Preparation method of boron nitride crystal whisker

A technology of boron nitride and whiskers, which is applied in the field of preparation of boron nitride whiskers, can solve problems such as insufficient nitriding treatment, affecting the performance of boron nitride whiskers, and easy defects on the surface of whiskers, etc., to achieve performance excellent effect

Inactive Publication Date: 2011-05-11
SHANDONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] At present, the preparation of boron nitride whiskers usually adopts a one-time nitriding process, but when the boron nitride whiskers are prepared by a one-time nitriding process, the nitriding treatment is insufficient, and it is difficult to obtain accurate stoichiometric boron nitride crystals, and the surface of the whiskers is easy to exist. Defects affect the performance of boron nitride whiskers

Method used

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Examples

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preparation example Construction

[0007] The method for preparing boron nitride whiskers of the present invention includes the following steps:

[0008] 1. Weigh the nitrogen compound and the boron compound at a molar ratio of 1:2 to 5, and prepare a mixed aqueous solution with a concentration of 0.5 to 1 mol / l;

[0009] 2. Put the mixed aqueous solution prepared in step 1 into a constant temperature water bath, and react at a temperature of 40-60°C for 12-24 hours to prepare a boron nitride whisker precursor;

[0010] 3. Put the boron nitride whisker precursor prepared in step 2 into a drying box and dry it at a temperature of 80-100°C for 12-24 hours.

[0011] 4. Put the boron nitride whisker precursor dried in step 3 into an alumina crucible, calcinate in the air at 300-350°C for 2 to 4 hours, and then cool naturally.

[0012] 5. Put the boron nitride whisker precursor prepared in step 4 into a graphite crucible, and calcinate for 12-24 hours in an ammonia atmosphere at 750-1000°C, and then cool naturally to obtain a...

Embodiment 1

[0022] 1. Weigh melamine and boric acid at a molar ratio of 1:5, and prepare a mixed aqueous solution with a concentration of 0.7 mol / l;

[0023] 2. Put the mixed aqueous solution prepared in step 1 into a constant temperature water bath, and react at a temperature of 50°C for 24 hours to prepare a boron nitride whisker precursor;

[0024] 3. Put the boron nitride whisker precursor prepared in step 2 into a drying box and dry it at a temperature of 90°C for 12 hours.

[0025] 4. Put the boron nitride whisker precursor dried in step 3 into an alumina crucible, calcined in air at 350°C for 3 hours, and then naturally cool.

[0026] 5. Put the boron nitride whisker precursor prepared in step 4 into a graphite crucible, calcined in an ammonia atmosphere at 800°C for 14 hours, and then naturally cool to obtain a primary nitrided boron nitride whisker.

[0027] 6. Put the primary nitrided boron nitride whiskers obtained in step 5 into a graphite crucible, calcined in a nitrogen atmosphere at ...

Embodiment 2

[0030] 1. Weigh ammonium chloride and borax at a molar ratio of 1:3, and prepare a mixed aqueous solution with a concentration of 0.6 mol / l;

[0031] 2. Put the mixed aqueous solution prepared in step 1 into a constant temperature water bath, and react at a temperature of 60°C for 20 hours to prepare a boron nitride whisker precursor;

[0032] 3. Put the boron nitride whisker precursor prepared in step 2 into a drying box and dry it at a temperature of 80°C for 12 hours.

[0033] 4. The boron nitride whisker precursor dried in step 3 is put into an alumina crucible, calcined in air at 350°C for 2 hours, and then naturally cooled.

[0034] 5. Put the boron nitride whisker precursor prepared in step 4 into a graphite crucible, calcined in an ammonia atmosphere at 850°C for 12 hours, and then naturally cool to obtain a primary nitrided boron nitride whisker.

[0035] 6. Put the primary nitrided boron nitride whiskers obtained in step 5 into a graphite crucible, calcined in a nitrogen atmos...

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Abstract

A preparation method of boron nitride crystal whisker belongs to the technical field of materials. The preparation method comprises the following steps of: taking industrial pure nitrogen compound andboron compound solid powder as raw materials; fully dissolving and mixing; heating in water bath to form the mixture of nitride and boride; dehydrating and drying; and putting the mixture to go through nitrogen treatment by two times respectively at the temperature of 750-1000 DEG C and 1600-2000 DEG C in a graphite crucible to prepare the product. The boron nitride crystal whisker prepared by the method has the advantages of large slenderness ratio of whisker and regular appearance, simple preparation technology and easy realization of industrial production.

Description

Technical field [0001] The invention relates to a method for preparing boron nitride whiskers and belongs to the technical field of new materials. Background technique [0002] Boron nitride ceramics have low dielectric constant and dielectric loss, which are 3.2 and 0.2×10 respectively -3 , Its decomposition temperature is as high as 2640℃, and it has excellent thermal and electrical stability in a wide temperature range. It is a good wave-transmitting material. However, the radome made of single-phase boron nitride ceramics has a surface ablation temperature of as high as 3300°C under high-speed reentry conditions, which seriously increases the high-temperature dielectric constant and dielectric loss of boron nitride, showing an unusual Ordinary telemetry signal attenuation, therefore, single-phase boron nitride ceramic is difficult to be used as a radome material for ultra-high-speed aircraft. If boron nitride fibers or boron nitride whiskers are combined with other ceramic m...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C30B29/38C30B29/62
Inventor 张玉军龚红宇谭砂砾赵林范润华朱保鑫
Owner SHANDONG UNIV