Method for synthesizing cubic boron nitride by using Mg3N2 and CaH2

A technology of cubic boron nitride and hexagonal boron nitride, which is applied in chemical instruments and methods, nitrogen compounds, and ultra-high pressure application processes, etc., can solve problems such as low conversion rate, achieve high conversion rate, and be beneficial to industrial production. , the effect of low purity requirements

Inactive Publication Date: 2010-10-27
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

[0012] Raw materials choose Mg by weight ratio 3 N 2 : CaH 2 : hexagonal boron nitride = 7.5: 7.5: 85. Mg 3 N 2 and CaH 2 Mix evenly, then mix evenly with hexagonal boron nitride with a purity of 90% and pre-press it into a cylindrical shape, then put it into a graphite sleeve, keep the height of the raw material column equal to the height of the graphite tube or 0.5-1mm lower than the height of the graphite tube, Put it inside a pyrophyllite block to assemble into a crafting block. After preheating in an oven with a set temperature of 100° C. for 20 minutes, high-pressure synthesis was carried out on a six-sided top press. Under the conditions of temperature 1050°C and pressure 4.5GPa, heat preservation and pressure for 5 minutes, stop heating and take out the sample after the temperature drops. After acid-base purification treatment, yellow translucent cubic boron nitride crystals are obtained. The obtained cBN crystal has a higher crystal form integrity rate, and th...

Embodiment 2

[0014] Raw material ratio, assembly method, synthesis equipment, temperature, and pressure conditions are the same as in Example 1, and the heat preservation and pressure holding time is 3 minutes. The cBN crystal obtained after the sample is purified is the same as in Example 1, and the crystal particle size is slightly finer than that of Example 1. , cBN conversion rate 30 ~ 35%.

Embodiment 3

[0016] Raw material ratio, assembly mode, synthetic equipment and temperature, pressure condition are all the same as embodiment 1, and the heat preservation and pressure holding time is 8 minutes, and the cBN crystal obtained after the sample is purified is the same as embodiment 1, and the crystal particle size is thicker than embodiment 1 ( Granularity≥100 # accounted for about 50%), the crystal form integrity rate is high, and the cBN conversion rate is 40%.

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Abstract

The invention discloses a method for synthesizing cubic boron nitride by using Mg3N2 and CaH2, and belongs to the technical field of superhard material synthesis. The Mg3N2 is taken as a contact agent, the CaH2 is taken as an additive, and hexagonal boron nitride is taken as a raw material; and the method comprises the following steps of: uniformly mixing the hexagonal boron nitride, the Mg3N2 and the CaH2 in a weight ratio, prepressing the mixture and assembling into a synthetic block; maintaining the synthesis temperature of between 1,000 and 1,600 DEG C and the synthesis pressure of between 4.0 and 6.0GPa for 3 to 8 minutes; and performing chemical treatment to obtain yellow and semitransparent cubic boron nitride crystals with high crystalline form integrity rate. The contact agent and the additive used by the method have low requirement on the purity of the hexagonal boron nitride raw material, and the synthesized cubic boron nitride has high crystalline form integrity rate; and the method has the advantages of wide synthesis pressure and temperature ranges, high conversion rate and low cost and is favorable for industrial production.

Description

technical field [0001] The invention belongs to the technical field of superhard material synthesis, in particular to a method for synthesizing cubic boron nitride from hexagonal boron nitride under high temperature and high pressure Background technique [0002] Cubic boron nitride is a superhard material that does not exist in nature but can only be synthesized artificially. Because cubic boron nitride has a higher oxidation resistance temperature than diamond, higher chemical stability than diamond, and excellent characteristics such as no reaction with iron group elements at high temperatures, it can be used as abrasives and made into tools, grinding wheels, and honing bars. , It is widely used in the field of processing ferrous metals and other alloy materials. [0003] Synthesis under high temperature and high pressure is a common method for preparing cubic boron nitride. The existing synthesis methods usually use Li, Mg, Ca and other alkali metals and alkaline earth ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01J3/06C01B21/064
Inventor 郭伟力贾晓鹏马红安陈立学
Owner JILIN UNIV
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