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Method for producing cubic boron nitride

a technology of cubic boron nitride and boron nitride, which is applied in the direction of pressurized chemical processes, chemical apparatus and processes, chemical/physical processes, etc., can solve the problem of lower reactivity with solvents (catalysts), and achieve the effects of improving the handling ability of crude powders, reducing shrinkage, and increasing productivity

Inactive Publication Date: 2000-01-11
SHOWA DENKO KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

Furthermore, when amide and / or imide are used in combination with a metal, it is generally possible to obtain cBN at a higher conversion rate than when an amide or imide is used alone, even at a lower temperature and pressure.
Actually, the hBN and the amide and / or imide, or the amide and / or imide and metal(s), are preferably compacted at about 1-2 t / cm.sup.2 pressure, either separately or after being filled into the reaction container. This will have an effect of improving the handleability of the crude powders while increasing the productivity by reducing the amount of shrinkage in the reaction container.

Problems solved by technology

This is because too great a granularity may result in a lower reactivity with the solvent (catalyst).

Method used

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  • Method for producing cubic boron nitride

Examples

Experimental program
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Effect test

example 1

Lithium amide and magnesium amide were added to hexagonal boron nitride with a granularity of 150 mesh or lower and containing, as impurities, 0.8 wt % of oxygen and 0.2 wt % of a metal impurity other than an alkali metal or alkaline earth metal, at an atomic ratio of 10 parts each of lithium and magnesium to 100 parts of the boron atoms in the compound. This mixture was subjected to 1.5 ton / cm.sup.2 pressure to make a 26 mm.phi..times.32 mmh compact, which was kept in the reaction container shown in FIG. 1.

In the reaction container shown in FIG. 1, the outer wall 1 of the container is made of pyrophyllite as a pressure conveyor, and is a cylindrically shaped, while the inner side thereof is provided with a heater 2 consisting of a graphite cylinder and pyrophyllite 8 as a partitioning material. Also, the top and bottom ends of the container are each provided with a conducting steel ring 3 and a conducting steel plate 4, while the inner sides thereof are provided with a sintered alu...

example 2

Lithium amide and calcium amide were added to hexagonal boron nitride at an atomic ratio of 10 parts lithium and 10 parts calcium to 100 parts of the boron atoms in the compound, to synthesize cubic boron nitride in the same manner as in Example 1, and upon evaluation the conversion rate to cubic boron nitride was found to be 91%.

example 3

Lithium imide and magnesium imide were added to hexagonal boron nitride at an atomic ratio of 10 parts lithium and 10 parts magnesium to 100 parts of the boron atoms in the compound, to synthesize cubic boron nitride in the same manner as in Example 1, and upon evaluation the conversion rate to cubic boron nitride was found to be 95%.

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Abstract

hBN is converted to cBN by keeping it under temperature and pressure conditions within the range of stability of cubic boron nitride, in the presence of a mixture of at least two compounds selected from amides and imides of Li, Ca and Mg, or in its copresence with at least one metal selected from elements of Groups Ia, IIa, IIIa, VIa, VIIa, VIII, IIb and IIIb.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to an improved method of synthesizing cubic boron nitride from hexagonal boron nitride.2. Description of the Related ArtCubic boron nitride is second only to diamond in hardness but has a greater chemical stability, and therefore it is becoming increasingly more important as a grinding, polishing and cutting material. A variety of methods have been proposed for producing cubic boron nitride, but the most well-known of these, which is widely used industrially, is a method of converting hexagonal boron nitride to cubic boron nitride under the high-temperature, high-pressure conditions of about 5.5 GPa and 1600.degree. C. in the presence of a solvent (catalyst). The well-known solvents (catalysts) for this method have conventionally been nitrides and boronitrides of alkali metals and alkaline earth metals. Of these, lithium-type solvents (catalysts) have been thoroughly studied, and lithium nitride and li...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): C01B21/00C01B21/064B01J3/06C04B35/5831
CPCB01J3/062B01J2203/0645B01J2203/066B01J2203/068C04B35/5831
Inventor SHIOI, KOUSUKENAKANO, HIDEFUMI
Owner SHOWA DENKO KK