CN1176009C

CN1176009C - Synthesis of cubic born nitride

Info

Publication number: CN1176009C
Application number: CNB021164592A
Authority: CN
Inventors: 马贤峰; 阎学伟; 赵伟; 崔硕景
Original assignee: Changchun Institute of Applied Chemistry of CAS
Current assignee: Changchun Institute of Applied Chemistry of CAS
Priority date: 2002-04-05
Filing date: 2002-04-05
Publication date: 2004-11-17
Anticipated expiration: 2022-04-05
Also published as: CN1370737A

Abstract

The present invention belongs to a method of synthesizing cubic boron nitride, which takes a mixture of LiNH2 and LiH as a catalyst, and takes rough hexagon boron nitride as raw material. The preload formed catalyst and the raw material are synthesized for 3 to 8 minutes in a condition of a high temperature of 1350 to 1800 DEG C, a resultant pressure is from 4.0 to 5.5 GPa, 70 to 80 meshes of cBN whose crushing strength is more than 35 newton can be obtained after the catalyst and the raw material are purified by melting sodium carbonate. The present invention has the characteristics of wide composite zone, short synthesizing time and high yield.

Description

The synthetic method of cubic boron nitride

Technical field: the method that the invention belongs to cubic boron nitride.

Background technology: cubic boron nitride (to call cBN in the following text) is that hardness is only second to and adamantine superhard material.Because cBN has than the high heat shock resistance of diamond and resistance of oxidation and the unreactiveness that do not react with iron family element ting, can be made into the processing that abrasive material, emery wheel, oilstone etc. are used for the high rigidity Ferrious material.The cBN cutter has advantages such as high rigidity, not sticking cutter, working accuracy height, long service life, is more suitable for the high speed and the precision sizing of material, to satisfy the demand of modern industrial technology development.As super hard abrasive, grinding tool, cutter material, cBN obtains to use in a lot of fields.

Since the synthetic first cBN of nineteen fifty-seven Wentorf, the study on the synthesis of cBN monocrystal comes into one's own always.High Temperature High Pressure catalyst method is the main method of synthetic cBN, and is used for the production of product, and catalyst plays crucial effect in synthetic.Basic metal, alkaline-earth metal and nitride thereof can be made catalyst, but, crystal grain ateliosis many with these catalyst material synthetic cBN micro mist, crystalline form are poor, crystal stock and inclusion is many, crushing strength is low.Ternary nitrogen boride Li ₃BN ₃, Ca ₃B ₂N ₄, Mg ₃BN ₃, Sr ₃B ₂N ₄, Ba ₃B ₂N ₄Can obtain the few transparent cBN of high strength, impurity and inclusion Deng making catalyst, but synthetic district is narrow, poor repeatability, product fine size, is not suitable for suitability for industrialized production.The clear 56-140013 of Japanese Patent uses Ca during clear 56-140014 is disclosed to be entitled as " synthetic method of cubic boron nitride " ₃B ₂N ₄With Li ₃N, Mg ₃N ₂, or Li ₃BN ₃The blended catalyst material has obtained the product of high strength, low impurity content, equivalance shape.But in fact this catalyst requires high to the purity of raw material hexagonal boron nitride (to call hBN in the following text) and degree of crystallinity: when hBN purity greater than 99.8%, boron oxide content is less than 0.1%, the greying index is less than 2 o'clock, can obtain high strength, transparent product of single crystal; When hBN purity less than 98%, boron oxide content is higher than 0.15%, the greying index can only obtain granularity less than 300 purpose micro powder grade cBN greater than 3 the time, and transformation efficiency is very low.

Summary of the invention: the purpose of this invention is to provide the synthetic method of a kind of cBN, by selecting LiNH ₂Make catalyst with the mixture of LiH, rough hBN is a raw material, the cBN of synthesizing high-strength, transparent, equivalance shape under lower synthesis pressure and temperature, and also synthetic district is wide, generated time is short, yield is high.In catalyst mixture, LiNH ₂Contribution to the cBN nucleation is bigger, uses LiNH separately ₂Can only obtain fine grain product.The nucleation amount has been controlled in the adding of LiH effectively, and promotes the g and D of cBN monocrystalline.Simultaneously, also boron oxide impurity is to the influence of cBN synthetic in the raw material to eliminating for LiH, and inclusion and defective play an important role in the minimizing product.

The present invention selects LiNH ₂Make catalyst with the mixture of LiH, the rough hexagonal boron nitride of selecting purity 96%～99.8%, boron oxide content 0.01%～0.48%, greying index 1～6 is as synthesis material, LiNH ₂After mixing by weight 6～12: 1 with LiH, mix by weight 1: 7～12 with the hBN raw material again, pre-molding is after High Temperature High Pressure is synthetic, synthesis temperature is 1350～1800 ℃, synthesis pressure is 4.0～5.5GPa, generated time is 3～8 minutes, and purifying with fusion yellow soda ash obtains cBN, and 70～80 purpose crushing strengths are more than 35 newton.

Embodiment is as follows:

Embodiment 1: with LiNH ₂After LiH mixes by 12: 1 weight ratios, again with purity 96%, to be 6 hBN pack in the tubular graphene heating element by weight being pressed into right cylinder at 1: 12 behind the mixing for boron oxide content 0.48%, greying index, after the high pressure assembling, High Temperature High Pressure is synthetic on 6 * 800 tons of six-plane piercer.Synthesis pressure 4.0Gpa, 1350 ℃ of temperature, generated time 5 minutes.Stop heating then, sample is taken out in release.Obtain cBN monocrystal amber, transparent, equivalance shape with the purification of fusion yellow soda ash, the transformation efficiency of cBN is 15%, size-grade distribution 100～400 orders.

Embodiment 2: with LiNH ₂After LiH mixed by 6: 1 weight ratios, again with purity 98%, boron oxide content 0.2%, greying index were that 4 hBN mixes by 1: 9 weight ratio, and it is synthetic to press the identical method High Temperature High Pressure of embodiment 1.Synthesis pressure 4.5Gpa, 1700 ℃ of temperature, generated time 5 minutes.Obtain amber, transparent, equivalance shape cBN monocrystal with the purification of fusion yellow soda ash, the transformation efficiency of cBN is 30%, size-grade distribution 60～350 orders, and wherein 140 orders are 35 newton with the crushing strength that slightly accounts for 30%, 70/80 order sample.

Embodiment 3: with LiNH ₂After LiH mixes by 9: 1 weight ratios, again with embodiment 2 in used hBN mixed by weight 1: 7, press embodiment 1 identical method High Temperature High Pressure and synthesize.Synthesis pressure 4.7Gpa, 1700 ℃ of temperature, generated time 5 minutes.Purification obtains amber equivalance shape cBN monocrystal, and the transformation efficiency of cBN is 35%, size-grade distribution 60～350 orders, and wherein 140 orders are 35 newton with the crushing strength that slightly accounts for 45%, 70/80 order sample.

Embodiment 4: with LiNH ₂After LiH mixes by 10: 1 weight ratios, again with embodiment 2 in used hBN mixed by weight 1: 8, press embodiment 1 identical method High Temperature High Pressure and synthesize.Synthesis pressure 5.0Gpa, 1700 ℃ of temperature, generated time 8 minutes.Purification obtains amber cBN monocrystal, and the transformation efficiency of cBN is 40%, size-grade distribution 60～350 orders, and wherein 140 orders are 37 newton with the crushing strength that slightly accounts for 50%, 70/80 order sample.

Embodiment 5: with LiNH ₂After LiH mixed by 10: 1 weight ratios, again with purity 99.8%, boron oxide content 0.01%, greying index were 1 hBN mixing in 1: 8 by weight, press embodiment 1 identical method High Temperature High Pressure and synthesize.Synthesis pressure 5.5Gpa, 1800 ℃ of temperature, generated time 3 minutes.Purification obtains amber cBN monocrystal, and the transformation efficiency of cBN is 32%, size-grade distribution 60～400 orders, and wherein 140 orders are 35 newton with the crushing strength that slightly accounts for 40%, 70/80 order sample.

Claims

1. the synthetic method of a cubic boron nitride is characterized in that selecting LiNH ₂Make catalyst with the mixture of LiH, the rough hexagonal boron nitride of selecting purity 96%～99.8%, boron oxide content 0.01%～0.48%, greying index 1～6 is as synthesis material, LiNH ₂After mixing by weight 6～12: 1 with LiH, mix by weight 1: 7～12 with the hexagonal boron nitride raw material again, pre-molding is after High Temperature High Pressure is synthetic, synthesis temperature is 1350～1800 ℃, synthesis pressure is 4.0～5.5GPa, generated time is 3～8 minutes, and purifying with fusion yellow soda ash obtains cubic boron nitride 70～80 orders, and crushing strength is more than 35 newton.