Method of synthesizing cubic boron nitride using alkali earth metal fluoride

A technology of cubic boron nitride and alkaline earth metals, applied in chemical instruments and methods, nitrogen compounds, non-metallic elements, etc., can solve the problems of low conversion rate and achieve high crystal integrity rate, short synthesis time and low synthesis temperature Effect

Inactive Publication Date: 2008-06-04
JILIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the catalyst used in this method has higher requirements on the purity and impurity content of hexagonal boron nitride. Only when the purity of hexagonal boron nitride is >99.8%, the content of boron oxide is <0.1%, and the graphitization index is <2 can a good synthesis be obtained. As a result, if the purity of hexagonal boron nitride is less than 98%, the content of boron oxide is greater than 0.15%, and the graphitization index is greater than 3, the particle size of cubic boron nitride obtained is less than 300 mesh, and the conversion rate is also very low.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0013] CaF 2 , Li 3 N and LiH are mixed evenly in a weight ratio of 1:4:1, and then mixed with hexagonal boron nitride with a purity of 95% in a weight ratio of 15:85 and pre-pressed into a cylindrical shape and then loaded into a graphite sleeve to maintain the height of the raw material column It is equal to the height of the graphite tube or 0.5-1mm lower than the height of the graphite tube, put it into a pyrophyllite block to assemble a synthetic block, and perform high-pressure synthesis on a six-sided top press. Under the conditions of 1100°C and 4.5GPa, heat preservation and pressure for 5 minutes, stop heating and take out the sample after the temperature drops, and obtain red-yellow transparent cubic boron nitride crystals after acid-base purification treatment. The obtained cBN crystals have high crystal form integrity , The conversion rate of cBN is 35-40%.

[0014] CaF 2 with MgF 2 Alternatively, according to the above raw material ratio, assembly, synthesis, ...

Embodiment 2

[0016] Sample proportioning, assembly, synthesis equipment, and temperature and pressure conditions are all the same as in Example 1, and the heat preservation and pressure holding time is 3 minutes. The cBN crystal obtained after the experimental sample is purified is the same as in Example 1, only the particle size is slightly finer, and the cBN conversion rate is 30% to 40%.

Embodiment 3

[0018] The sample preparation and synthesis conditions are the same as in Example 1, and the heat preservation and pressure holding time is 8 minutes. The cBN crystals obtained after the purification of the synthetic product are the same as in Example 1. The crystal particle size is relatively coarse, the crystal form integrity rate is high, and the cBN conversion rate is 35-40%. .

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PUM

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Abstract

A process for synthesizing the cubic boron nitride from the fluoride of alkali-earth metal includes such steps as mixing hexagonal boron nitride, the mixture of CaF2 and / or MgF2 and LisN, and LiH, die pressing, assembling to become block in graphite pipe, synthesizing and heat treating.

Description

technical field [0001] The invention belongs to the field of high-temperature and high-pressure synthesis methods for superhard materials, and in particular relates to a method for selecting a new catalyst to synthesize cubic boron nitride. Background technique [0002] The hardness of cubic boron nitride (cBN) is second only to diamond, because it has a higher oxidation resistance temperature than diamond, and has excellent characteristics such as not reacting with iron group elements at high temperatures, it can be used as abrasives and made into tools, grinding wheels and Products such as honing rods have been widely used in the processing of high-hardness steel and its alloy materials. [0003] Mixing hexagonal boron nitride (hBN) with a catalyst and synthesizing under high temperature and high pressure is a common method for preparing cubic boron nitride. The general cubic boron nitride synthesis method uses Li, Mg, Ca and other alkali metals and alkaline earth metals ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B01J3/06C01B21/064
Inventor 郭伟力贾晓鹏马红安陈立学卜雨洲邹广田
Owner JILIN UNIV
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