CN107523875B - Cubic boron nitride single crystal and preparation method thereof - Google Patents
Cubic boron nitride single crystal and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a preparation method of cubic boron nitride single crystal, which comprises the following steps: weighing hexagonal boron nitride powder, Mg-Al alloy powder and feldspar powder, uniformly mixing, and pressing into a synthetic column; synthesizing the synthetic column at high temperature and high pressure to obtain a black cubic boron nitride crystal crude product; crushing to obtain a massive cubic boron nitride crystal crude product, and performing acid treatment, alkali treatment, drying and screening to obtain a cubic boron nitride crystal finished product. The invention realizes the control of the granularity and other properties of the synthesized cubic boron nitride by mainly controlling the content of feldspar powder in the synthetic raw material. The preparation method of the cubic boron nitride crystal provided by the invention can synthesize the cubic boron nitride with the granularity range of 60-140 meshes and in a fine range. The cubic boron nitride can be applied to preparing cubic boron nitride polycrystal and composite sheets, cubic boron nitride superhard grinding wheels and grinding products.
Description
Technical Field
The invention belongs to the technical field of manufacturing of superhard materials, and particularly relates to a method for synthesizing cubic boron nitride by using nonmetallic minerals as additives.
Background
Cubic boron nitride, whose molecular formula is BN, was first developed by r.h. wintoff in the united states in 1957, and its crystal structure resembles diamond. Cubic boron nitride is generally synthesized from hexagonal boron nitride and a catalyst at high temperature and high pressure. The cubic boron nitride has excellent performances of high hardness, thermal stability, chemical inertness, good red-transparent appearance, wider forbidden bandwidth and the like, the hardness of the cubic boron nitride crystal is only inferior to that of diamond, but the thermal stability is far higher than that of the diamond, the cubic boron nitride crystal has larger chemical stability on iron-series metal elements, and the cubic boron nitride crystal is commonly used as an abrasive and a cutter material. The cubic boron nitride grinding tool has excellent grinding performance, is not only suitable for processing difficult-to-grind materials, improves the production efficiency, but also can effectively improve the grinding quality of workpieces. The use of cubic boron nitride crystals is a great contribution to metal working, leading to revolutionary changes in grinding, and is the second leap in grinding technology. Cubic boron nitride is widely applied as a superhard abrasive in the processing fields of different industries, and is now an indispensable important material for automobiles, aerospace, machinery, electronics, microelectronics and the like, so that great attention is paid to developed countries of various industries.
The main method for synthesizing cubic boron nitride single crystal at present is to use hexagonal boron nitride and catalyst, the catalyst can be alkali metal, alkaline earth metal simple substance or alloy, or alkali metal, alkaline earth metal nitride and boronitride, and a certain amount of additive containing hydrogen or ammonia is added, and the hexagonal boron nitride is converted into cubic boron nitride under the condition of high temperature and high pressure. However, in the production process, the additive containing hydrogen or ammonia is very easy to react with partial substances in the air, so that gases harmful to human health are emitted, and the additive containing hydrogen or ammonia is also extremely harmful to human bodies after being contacted or inhaled by human bodies. Therefore, it is of great value to develop a method for synthesizing cubic boron nitride single crystal by using non-toxic and harmless additives.
The main influencing factors in the process of synthesizing the cubic boron nitride are pressure and temperature, the main equipment for synthesizing the cubic boron nitride single crystal at present is a cubic press, and the pressure generated by the cubic press is transmitted into a synthesis cavity so as to form the pressure condition required by the conversion of the cubic boron nitride in the synthesis cavity. Generally, the pressure transmission efficiency of the same substance in the gas state and the liquid state is superior to that in the solid state. If gaseous or liquid substances can be generated in the synthesis cavity, the pressure transmission efficiency of pressure in the synthesis cavity can be improved, the service pressure of equipment is directly reduced, the service life of the equipment is prolonged, and the production efficiency is improved. However, when gaseous substances are introduced into the synthesis cavity, the difficulty of sealing is increased, and once the sealing is not tight, production accidents such as blasting and the like can be caused. For example, gaseous species are generated in the synthesis chamber when additives containing hydrogen or ammonia are added, but the consumption of the cemented carbide anvil is higher when the additives are used for production than other methods.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for synthesizing cubic boron nitride by using non-metallic ore as an additive, wherein in the synthesis process, non-toxic and harmless additives of albite and potash feldspar are introduced, and the pressure transmission efficiency is improved by utilizing the fact that the albite and the potash feldspar are converted into liquid during synthesis.
The object of the invention is achieved in the following way:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) weighing 60-85 parts of hexagonal boron nitride powder, 5-35 parts of Mg-Al alloy powder and 1-15 parts of feldspar powder according to the mass parts, uniformly mixing, and pressing into a synthetic column;
(2) applying the synthesis pressure of 75-80MPa to the synthesis column obtained in the step (1) at 1300-;
(3) and crushing the obtained cubic boron nitride crystal crude product to obtain a blocky cubic boron nitride crystal crude product, and performing acid treatment, alkali treatment, drying and screening on the blocky cubic boron nitride crystal crude product to obtain a cubic boron nitride crystal finished product.
The feldspar powder in the step (1) consists of albite powder and potassium feldspar powder, and the mass ratio of the albite powder to the potassium feldspar powder is 1:4-1: 2.
The step (1) is specifically as follows: weighing the raw materials according to the mass parts, firstly adding 50% of hexagonal boron nitride powder into a mixer, then adding Mg-Al alloy powder, albite powder and potash feldspar powder into the mixer, and finally adding the rest hexagonal boron nitride powder into the mixer to be uniformly mixed; vacuum packaging the obtained mixed powder, extruding and granulating under 200-300 MPa by using a cold isostatic press, crushing by using a jaw crusher after granulation is finished, screening by using an 80-mesh screen to obtain granules for preparing the synthetic column, and pressing the obtained granules into the synthetic column under 10-20MPa by using a full-automatic oil press; the synthetic column, the heating carbon tube and the heat-insulating ceramic sheet component are assembled into a synthetic rod, and the synthetic rod is stored in a vacuum environment for standby before synthesis.
The hexagonal boron nitride powder is subjected to high-temperature treatment at 200 ℃ for 2 hours before use, is subjected to heat preservation at 120 ℃ for standby, and is dried in vacuum before use.
The step (2) is specifically as follows: the synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 45-50MPa at a boosting speed of 0.8-1.2MPa/s for one time, maintaining the pressure for 2min, then boosting the pressure to 75-80MPa at the same boosting speed at one time, starting heating when the pressure is raised to 35-38MPa in the boosting process, raising the temperature to 1300 plus 1800K within 2-4min, keeping the temperature for 8-15min, finally, reducing the temperature and the pressure, taking out pyrophyllite blocks and cracking to obtain the cubic boron nitride single crystal synthesis column.
Wherein, the first step of boosting pressure to 45-50MPa at a boosting rate of 0.8-1.2MPa/s and maintaining the pressure for 2min is to control the nucleation number of the cubic boron nitride in the synthetic cavity. Then, the pressure is increased to 75-80MPa at the same pressure increasing speed in one step so as to promote the cubic boron nitride single crystal to enter a high-pressure excellent crystal growth area to the maximum extent. The constant temperature and pressure of the step (2) is 8-15min to ensure that the boron nitride grows for a certain time after nucleation and the synthesized boron nitride reaches the required granularity, and the constant temperature and pressure refers to maintaining the pressure in the high-pressure cavity to reach the pressure and temperature of 75-80MPa of the synthesis pressure.
The step (3) is specifically as follows: crushing and ball-milling the cubic boron nitride crude product by using a jaw crusher and a ball mill to obtain powdery cubic boron nitride crystal crude product; preparing mixed acid of concentrated sulfuric acid with the mass concentration of 95-98% and concentrated nitric acid with the mass concentration of 63-65% according to the volume ratio of 4: 1; placing the powdery cubic boron nitride crystal crude product in the mixed acid, heating to 150 ℃ and 180 ℃, boiling for 4-6h, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in a sodium hydroxide solution with the mass concentration of 95-98%, heating to 180-280 ℃, boiling for 2-3h, repeatedly washing with water and drying to obtain the cubic boron nitride crystal crude product; and sequentially sorting the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with different particle sizes.
Crushing and ball-milling the cubic boron nitride crystal crude product by using a jaw crusher and a ball mill to obtain powdery cubic boron nitride crystal crude product specifically: crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain the powdery cubic boron nitride crystal.
In the step (3), the hot water is used for immersing the blocky particles and continuously stirring, so that the hot water can partially dissolve the hexagonal boron nitride which is not converted and synthesized in the synthesis rod, and the hexagonal boron nitride is easier to ball mill and break in the subsequent ball milling process. The cubic boron nitride is treated by mixed acid of concentrated sulfuric acid with the concentration of 95-98% and concentrated nitric acid with the concentration of 63-65% prepared according to the volume ratio of 4:1, so that impurities, such as graphite, metal and the like, introduced in the cubic boron nitride due to synthesis and ball milling are treated. The purpose of treating cubic boron nitride with 95-98% sodium hydroxide is to treat impurities introduced by synthesis and other links in cubic boron nitride, such as silicon oxide, aluminum oxide, pyrophyllite and unconverted and synthesized hexagonal boron nitride.
The cubic boron nitride single crystal is prepared by the preparation method of the cubic boron nitride single crystal.
Under the condition of the same synthesis temperature and synthesis pressure, the cubic boron nitride crystals obtained are different along with different proportions of the raw material components. Specifically, when the mixed raw materials comprise 80-85 parts of hexagonal boron nitride, 5-10 parts of Mg-Al alloy powder and 13-15 parts of feldspar powder, the particle size of the synthesized cubic boron nitride is mainly concentrated in a fine range of 120-140 meshes. When the mixed raw materials comprise 75-80 parts of hexagonal boron nitride, 10-15 parts of Mg-Al alloy powder and 10-12 parts of feldspar powder, the particle size of the synthesized cubic boron nitride is mainly concentrated in the ranges of 100-120 meshes, 120-140 meshes and fine range. When the mixed raw materials comprise 70-75 parts of hexagonal boron nitride, 15-20 parts of Mg-Al alloy powder and 7-9 parts of feldspar powder, the particle size of the synthesized cubic boron nitride is mainly concentrated in 80-100 meshes, 100-120 meshes, 120-140 meshes and fine ranges. When the mixed raw materials are 65-70 parts of hexagonal boron nitride, 20-25 parts of Mg-Al alloy powder and 4-6 parts of feldspar powder, the particle size of the synthesized cubic boron nitride is mainly concentrated in 70-80 meshes, 80-100 meshes, 100-120 meshes, 120-140 meshes and in a fine range. When the mixed raw materials comprise 60-65 parts of hexagonal boron nitride, 25-35 parts of Mg-Al alloy powder and 1-3 parts of feldspar powder, the particle size of the synthesized cubic boron nitride is mainly concentrated in 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-120 meshes, 120-140 meshes and a fine range.
The invention realizes the control of the granularity and other properties of the synthesized cubic boron nitride by mainly controlling the content of feldspar powder in the synthetic raw material. The preparation method of the cubic boron nitride crystal provided by the invention can synthesize the cubic boron nitride with the particle size range of 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-120 meshes, 120-140 meshes and in a fine range. The cubic boron nitride can be applied to preparing cubic boron nitride polycrystal and composite sheets, cubic boron nitride superhard grinding wheels and grinding products.
Detailed Description
Example 1:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) weighing 60-85 parts of hexagonal boron nitride powder, 5-35 parts of Mg-Al alloy powder and 1-15 parts of feldspar powder according to the mass parts, uniformly mixing, and pressing into a synthetic column;
(2) applying the synthesis pressure of 75-80MPa to the synthesis column obtained in the step (1) at 1300-;
(3) and crushing the obtained cubic boron nitride crystal crude product to obtain a blocky cubic boron nitride crystal crude product, and performing acid treatment, alkali treatment, drying and screening on the blocky cubic boron nitride crystal crude product to obtain a cubic boron nitride crystal finished product.
The feldspar powder in the step (1) consists of albite powder and potassium feldspar powder, and the mass ratio of the albite powder to the potassium feldspar powder is 1:4-1: 2.
The step (1) is specifically as follows: weighing the raw materials according to the mass parts, firstly adding 50% of hexagonal boron nitride powder into a mixer, then adding Mg-Al alloy powder, albite powder and potash feldspar powder into the mixer, and finally adding the rest hexagonal boron nitride powder into the mixer to be uniformly mixed; vacuum packaging the obtained mixed powder, extruding and granulating under 200-300 MPa by using a cold isostatic press, crushing by using a jaw crusher after granulation is finished, screening by using an 80-mesh screen to obtain granules for preparing the synthetic column, and pressing the obtained granules into the synthetic column under 10-20MPa by using a full-automatic oil press; the synthetic column, the heating carbon tube and the heat-insulating ceramic sheet component are assembled into a synthetic rod, and the synthetic rod is stored in a vacuum environment for standby before synthesis.
The hexagonal boron nitride powder is subjected to high-temperature treatment at 200 ℃ for 2 hours before use, is subjected to heat preservation at 120 ℃ for standby, and is dried in vacuum before use.
The step (2) is specifically as follows: the synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 45-50MPa at a boosting speed of 0.8-1.2MPa/s for one time, maintaining the pressure for 2min, then boosting the pressure to 75-80MPa at the same boosting speed at one time, starting heating when the pressure is raised to 35-38MPa in the boosting process, raising the temperature to 1300 plus 1800K within 2-4min, keeping the temperature for 8-15min, finally, reducing the temperature and the pressure, taking out pyrophyllite blocks and cracking to obtain the cubic boron nitride single crystal synthesis column.
The step (3) is specifically as follows: crushing and ball-milling the cubic boron nitride crude product by using a jaw crusher and a ball mill to obtain powdery cubic boron nitride crystal crude product; preparing mixed acid of concentrated sulfuric acid with the mass concentration of 95-98% and concentrated nitric acid with the mass concentration of 63-65% according to the volume ratio of 4: 1; placing the powdery cubic boron nitride crystal crude product in the mixed acid, heating to 150 ℃ and 180 ℃, boiling for 4-6h, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in a sodium hydroxide solution with the mass concentration of 95-98%, heating to 180-280 ℃, boiling for 2-3h, repeatedly washing with water and drying to obtain the cubic boron nitride crystal crude product; and sequentially sorting the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with different particle sizes.
Crushing and ball-milling the cubic boron nitride crystal crude product by using a jaw crusher and a ball mill to obtain powdery cubic boron nitride crystal crude product specifically: crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain the powdery cubic boron nitride crystal.
The cubic boron nitride single crystal is prepared by the preparation method of the cubic boron nitride single crystal.
Example 2:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) the hexagonal boron nitride powder is subjected to high-temperature treatment at 200 ℃ for 2 hours before use, is subjected to heat preservation at 120 ℃ for standby, and is dried in vacuum before use. Weighing 60kg of hexagonal boron nitride powder, 5kg of Mg-Al alloy powder and 1kg of feldspar powder, wherein the feldspar powder consists of albite powder and potassium feldspar powder, and the mass ratio of the albite powder to the potassium feldspar powder is 1: 4; adding 50% of hexagonal boron nitride powder into a mixer, adding Mg-Al alloy powder, albite powder and potash feldspar powder into the mixer, and adding the rest hexagonal boron nitride powder into the mixer to be uniformly mixed; vacuum packaging the obtained mixed powder, extruding and granulating by using a cold isostatic press under the pressure of 200MPa, crushing by using a jaw crusher after granulation is finished, screening by using a 80-mesh screen to obtain granules for preparing the synthetic column, and pressing the obtained granules into the synthetic column under the pressure of 10MPa by using a full-automatic oil press; the synthetic column, the heating carbon tube and the heat-insulating ceramic sheet component are assembled into a synthetic rod, and the synthetic rod is stored in a vacuum environment for standby before synthesis.
(2) The synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 45MPa at one time at a boosting speed of 0.8MPa/s, maintaining the pressure for 2min, then boosting the pressure to 75MPa at one time at the same boosting speed, starting heating when the pressure is raised to 35MPa in the boosting process, raising the temperature to 1300K within 2min, keeping the temperature for 8min, finally cooling and reducing the pressure, taking out pyrophyllite blocks and cracking the pyrophyllite blocks to obtain the cubic boron nitride single crystal synthetic column.
(3) Crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain powdery cubic boron nitride crystals; preparing mixed acid of concentrated sulfuric acid with the mass concentration of 95% and concentrated nitric acid with the mass concentration of 63% according to the volume ratio of 4: 1; putting the powdery cubic boron nitride crystal crude product into the mixed acid, heating to 150 ℃, boiling for 4 hours, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in a sodium hydroxide solution with the mass concentration of 95%, heating to 180 ℃, boiling for 2 hours, repeatedly washing with water, and drying to obtain the cubic boron nitride crystal crude product; then screening the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with the particle sizes of 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-120 meshes and 120-140 meshes or smaller.
Example 3:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) the hexagonal boron nitride powder is subjected to high-temperature treatment at 200 ℃ for 2 hours before use, is subjected to heat preservation at 120 ℃ for standby, and is dried in vacuum before use. Weighing 65kg of hexagonal boron nitride powder, 10kg of Mg-Al alloy powder and 5kg of feldspar powder, wherein the feldspar powder consists of albite powder and potassium feldspar powder, and the mass ratio of the albite powder to the potassium feldspar powder is 2: 7; adding 50% of hexagonal boron nitride powder into a mixer, adding Mg-Al alloy powder, albite powder and potash feldspar powder into the mixer, and adding the rest hexagonal boron nitride powder into the mixer to be uniformly mixed; vacuum packaging the obtained mixed powder, extruding and granulating by using a cold isostatic press under the pressure of 220MPa, crushing by using a jaw crusher after granulation is finished, screening by using a 80-mesh screen to obtain granules for preparing the synthetic column, and pressing the obtained granules into the synthetic column under the pressure of 12MPa by using a full-automatic oil press; the synthetic column, the heating carbon tube and the heat-insulating ceramic sheet component are assembled into a synthetic rod, and the synthetic rod is stored in a vacuum environment for standby before synthesis.
(2) The synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 46MPa at one time at a boosting speed of 0.9MPa/s, maintaining the pressure for 2min, then boosting the pressure to 76MPa at one time at the same boosting speed, starting heating when the pressure is raised to 35.5MPa in the boosting process, raising the temperature to 1400K within 2.5min, keeping the temperature for 9min, finally, reducing the temperature and the pressure, taking out pyrophyllite blocks, and smashing to obtain the cubic boron nitride single crystal synthetic column.
(3) Crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain powdery cubic boron nitride crystals; preparing mixed acid of concentrated sulfuric acid with the mass concentration of 95.5% and concentrated nitric acid with the mass concentration of 63.5% according to the volume ratio of 4: 1; putting the powdery cubic boron nitride crystal crude product into the mixed acid, heating to 155 ℃, boiling for 4.5 hours, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in a sodium hydroxide solution with the mass concentration of 95.5%, heating to 200 ℃, boiling for 2.2 hours, repeatedly washing with water, and drying to obtain the cubic boron nitride crystal crude product; then screening the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with the particle sizes of 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-120 meshes and 120-140 meshes or smaller.
Example 4:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) the hexagonal boron nitride powder is subjected to high-temperature treatment at 200 ℃ for 2 hours before use, is subjected to heat preservation at 120 ℃ for standby, and is dried in vacuum before use. Weighing 70kg of hexagonal boron nitride powder, 15kg of Mg-Al alloy powder and 8kg of feldspar powder, wherein the feldspar powder consists of albite powder and potassium feldspar powder, and the mass ratio of the albite powder to the potassium feldspar powder is 1: 3; adding 50% of hexagonal boron nitride powder into a mixer, adding Mg-Al alloy powder, albite powder and potash feldspar powder into the mixer, and adding the rest hexagonal boron nitride powder into the mixer to be uniformly mixed; vacuum packaging the obtained mixed powder, extruding and granulating by using a cold isostatic press under the pressure of 240MPa, crushing by using a jaw crusher after granulation is finished, screening by using an 80-mesh screen to obtain granules for preparing the synthetic column, and pressing the obtained granules into the synthetic column under the pressure of 14MPa by using a full-automatic oil press; the synthetic column, the heating carbon tube and the heat-insulating ceramic sheet component are assembled into a synthetic rod, and the synthetic rod is stored in a vacuum environment for standby before synthesis.
(2) The synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 47MPa at one time at a boosting speed of 1.0MPa/s, maintaining the pressure for 2min, then boosting the pressure to 77MPa at one time at the same boosting speed, starting heating when the pressure is raised to 36MPa in the boosting process, raising the temperature to 1500K within 3min, keeping the temperature for 10min, finally cooling and reducing the pressure, taking out pyrophyllite blocks and cracking the pyrophyllite blocks to obtain the cubic boron nitride single crystal synthetic column.
(3) Crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain powdery cubic boron nitride crystals; preparing mixed acid of concentrated sulfuric acid with mass concentration of 96% and concentrated nitric acid with mass concentration of 64% according to the volume ratio of 4: 1; putting the powdery cubic boron nitride crystal crude product into the mixed acid, heating to 160 ℃, boiling for 5 hours, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in a sodium hydroxide solution with the mass concentration of 96%, heating to 220 ℃, boiling for 2.4 hours, repeatedly washing with water, and drying to obtain the cubic boron nitride crystal crude product; then screening the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with the particle sizes of 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-120 meshes and 120-140 meshes or smaller.
Example 5:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) the hexagonal boron nitride powder is subjected to high-temperature treatment at 200 ℃ for 2 hours before use, is subjected to heat preservation at 120 ℃ for standby, and is dried in vacuum before use. Weighing 75kg of hexagonal boron nitride powder, 20kg of Mg-Al alloy powder and 10kg of feldspar powder, wherein the feldspar powder consists of albite powder and potassium feldspar powder, and the mass ratio of the albite powder to the potassium feldspar powder is 2: 5; adding 50% of hexagonal boron nitride powder into a mixer, adding Mg-Al alloy powder, albite powder and potash feldspar powder into the mixer, and adding the rest hexagonal boron nitride powder into the mixer to be uniformly mixed; vacuum packaging the obtained mixed powder, extruding and granulating by using a cold isostatic press under the pressure of 260MPa, crushing by using a jaw crusher after granulation is finished, screening by using an 80-mesh screen to obtain granules for preparing the synthetic column, and pressing the obtained granules into the synthetic column under the pressure of 16MPa by using a full-automatic oil press; the synthetic column, the heating carbon tube and the heat-insulating ceramic sheet component are assembled into a synthetic rod, and the synthetic rod is stored in a vacuum environment for standby before synthesis.
(2) The synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 48MPa at one time at a boosting speed of 1.1MPa/s, maintaining the pressure for 2min, then boosting the pressure to 78MPa at one time at the same boosting speed, starting heating when the pressure is raised to 36.5MPa in the boosting process, raising the temperature to 1600K within 3.5min, keeping the temperature for 12min, finally reducing the temperature and the pressure, taking out the pyrophyllite block, and cracking to obtain the cubic boron nitride single crystal synthetic column.
(3) Crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain powdery cubic boron nitride crystals; preparing mixed acid of concentrated sulfuric acid with mass concentration of 96.5% and concentrated nitric acid with mass concentration of 64.5% according to the volume ratio of 4: 1; putting the powdery cubic boron nitride crystal crude product into the mixed acid, heating to 165 ℃ and boiling for 5.5 hours, and repeatedly washing and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in a sodium hydroxide solution with the mass concentration of 96.5%, heating to 240 ℃, boiling for 2.6 hours, repeatedly washing with water, and drying to obtain the cubic boron nitride crystal crude product; then screening the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with the particle sizes of 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-120 meshes and 120-140 meshes or smaller.
Example 6:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) the hexagonal boron nitride powder is subjected to high-temperature treatment at 200 ℃ for 2 hours before use, is subjected to heat preservation at 120 ℃ for standby, and is dried in vacuum before use. Weighing 80kg of hexagonal boron nitride powder, 30kg of Mg-Al alloy powder and 12kg of feldspar powder, wherein the feldspar powder consists of albite powder and potassium feldspar powder, and the mass ratio of the albite powder to the potassium feldspar powder is 4: 9; adding 50% of hexagonal boron nitride powder into a mixer, adding Mg-Al alloy powder, albite powder and potash feldspar powder into the mixer, and adding the rest hexagonal boron nitride powder into the mixer to be uniformly mixed; vacuum packaging the obtained mixed powder, extruding and granulating by using a cold isostatic press under the pressure of 280MPa, crushing by using a jaw crusher after granulation is finished, screening by using a 80-mesh screen to obtain granules for preparing a synthetic column, and pressing the obtained granules into the synthetic column under the pressure of 18MPa by using a full-automatic oil press; the synthetic column, the heating carbon tube and the heat-insulating ceramic sheet component are assembled into a synthetic rod, and the synthetic rod is stored in a vacuum environment for standby before synthesis.
(2) The synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 49MPa at one time at a boosting speed of 1.2MPa/s, maintaining the pressure for 2min, then boosting the pressure to 79MPa at one time at the same boosting speed, starting heating when the pressure is increased to 37MPa in the boosting process, raising the temperature to 1700K within 4min, keeping the temperature for 14min, finally cooling and reducing the pressure, taking out pyrophyllite blocks and cracking to obtain the cubic boron nitride single crystal synthesis column.
(3) Crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain powdery cubic boron nitride crystals; preparing mixed acid of concentrated sulfuric acid with the mass concentration of 97% and concentrated nitric acid with the mass concentration of 65% according to the volume ratio of 4: 1; putting the powdery cubic boron nitride crystal crude product into the mixed acid, heating to 170 ℃, boiling for 6 hours, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in 97% sodium hydroxide solution, heating to 260 ℃, boiling for 2.8h, repeatedly washing with water, and drying to obtain cubic boron nitride crystal crude product; then screening the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with the particle sizes of 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-120 meshes and 120-140 meshes or smaller.
Example 7:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) the hexagonal boron nitride powder is subjected to high-temperature treatment at 200 ℃ for 2 hours before use, is subjected to heat preservation at 120 ℃ for standby, and is dried in vacuum before use. Weighing 85kg of hexagonal boron nitride powder, 35kg of Mg-Al alloy powder and 15kg of feldspar powder, wherein the feldspar powder consists of albite powder and potassium feldspar powder, and the mass ratio of the albite powder to the potassium feldspar powder is 1: 2; adding 50% of hexagonal boron nitride powder into a mixer, adding Mg-Al alloy powder, albite powder and potash feldspar powder into the mixer, and adding the rest hexagonal boron nitride powder into the mixer to be uniformly mixed; vacuum packaging the obtained mixed powder, extruding and granulating by using a cold isostatic press under the pressure of 300MPa, crushing by using a jaw crusher after granulation is finished, screening by using a 80-mesh screen to obtain granules for preparing the synthetic column, and pressing the obtained granules into the synthetic column under the pressure of 20MPa by using a full-automatic oil press; the synthetic column, the heating carbon tube and the heat-insulating ceramic sheet component are assembled into a synthetic rod, and the synthetic rod is stored in a vacuum environment for standby before synthesis.
(2) The synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 50MPa at a boosting speed of 1.2MPa/s for 2min, then boosting the pressure to 80MPa at the same boosting speed at a time, heating when the pressure is raised to 38MPa in the boosting process, raising the temperature to 1800K within 4min, keeping the temperature for 15min, finally cooling and reducing the pressure, taking out pyrophyllite blocks and cracking to obtain the cubic boron nitride single crystal synthetic column.
(3) Crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain powdery cubic boron nitride crystals; preparing mixed acid of concentrated sulfuric acid with mass concentration of 98% and concentrated nitric acid with mass concentration of 65% according to the volume ratio of 4: 1; putting the powdery cubic boron nitride crystal crude product into the mixed acid, heating to 180 ℃, boiling for 6 hours, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in a sodium hydroxide solution with the mass concentration of 98%, heating to 280 ℃, boiling for 3 hours, repeatedly washing with water, and drying to obtain a cubic boron nitride crystal crude product; then screening the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with the particle sizes of 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-120 meshes and 120-140 meshes or smaller.
Example 8:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) firstly, the required hexagonal boron nitride is treated for 2 hours at a high temperature of 200 ℃, and is treated in a vacuum oven in vacuum before use and is stored for use. According to the mass percentage, 80kg of hexagonal boron nitride, 7kg of Mg-Al alloy powder and 13kg of feldspar powder are weighed by a 0.1g precision electronic balance, wherein the weight ratio of the albite powder: potassium feldspar powder =1: 2. Firstly, adding 1/2 required hexagonal boron nitride into a three-dimensional mixer, then adding 7kg of Mg-Al alloy powder and 13kg of feldspar powder into the mixer, and finally adding the remaining 1/2 hexagonal boron nitride into the three-dimensional mixer, wherein the mixing time is 2 hours. And taking out the mixture after the material mixing is finished, carrying out vacuum packaging on the mixture by using a vacuum packaging machine, and carrying out grinding and pelleting under the pressure of 200MPa by using a cold isostatic press. Crushing the granules by a jaw crusher after granulation is finished, sieving the granules by a 80-mesh sieve to obtain granules for preparing the synthetic column, pressing the obtained granules into a synthetic rod by a full-automatic four-column oil press under the pressure of 15MPa, assembling the heating carbon tube and the heat-insulating ceramic sheet component into the synthetic rod, and storing the synthetic rod in a vacuum environment for later use before synthesis.
(2) The synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 45MPa at one time at a boosting speed of 1.0MPa/s, maintaining the pressure for 2min, then boosting the pressure to 75MPa at one time at the same boosting speed, starting heating when the pressure is raised to 45MPa in the boosting process, raising the temperature to 1600K within 2.5min, keeping the temperature for 13min, finally reducing the temperature and the pressure, taking out pyrophyllite blocks and cracking to obtain the cubic boron nitride single crystal synthetic column.
(3) Crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain powdery cubic boron nitride crystals; preparing mixed acid of concentrated sulfuric acid with mass concentration of 96% and concentrated nitric acid with mass concentration of 64% according to the volume ratio of 4: 1; putting the powdery cubic boron nitride crystal crude product into the mixed acid, heating to 160 ℃, boiling for 5 hours, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in a sodium hydroxide solution with the mass concentration of 98%, heating to 260 ℃, boiling for 2 hours, repeatedly washing with water, and drying to obtain a cubic boron nitride crystal crude product; and screening the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with different particle sizes, such as 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-plus-120 meshes, 120-plus-140 meshes and the like. The granularity of the synthesized cubic boron nitride is mainly concentrated in a range of 120-140 meshes and in a fine range, and the average yield of the cubic boron nitride with the granularity is about 65 percent.
Example 9:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) firstly, the required hexagonal boron nitride is treated for 2 hours at a high temperature of 200 ℃, and is treated in a vacuum oven in vacuum before use and is stored for use. Weighing 75kg of hexagonal boron nitride, 14kg of Mg-Al alloy powder and 11kg of feldspar powder by using a 0.1g precision electronic balance according to the mass percentage, wherein the weight ratio of the albite powder: potassium feldspar powder =1: 2. Firstly, adding 1/2 required hexagonal boron nitride into a three-dimensional mixer, then adding 7kg of Mg-Al alloy powder and 13kg of feldspar powder into the mixer, and finally adding the remaining 1/2 hexagonal boron nitride into the three-dimensional mixer, wherein the mixing time is 2.5 hours. And taking out the mixture after the material mixing is finished, carrying out vacuum packaging on the mixture by using a vacuum packaging machine, and carrying out grinding and pelleting under the pressure of 250MPa by using a cold isostatic press. Crushing the granules by a jaw crusher after granulation is finished, sieving the granules by a 80-mesh sieve to obtain granules for preparing the synthetic column, pressing the obtained granules into a synthetic rod by a full-automatic four-column oil press under the pressure of 20MPa, assembling the heating carbon tube and the heat-insulating ceramic sheet component into the synthetic rod, and storing the synthetic rod in a vacuum environment for later use before synthesis.
(2) The synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 47MPa at one time at a boosting speed of 1.1MPa/s, maintaining the pressure for 2min, then boosting the pressure to 76MPa at one time at the same boosting speed, starting heating when the pressure is raised to 35MPa in the boosting process, raising the temperature to 1600K within 2min, keeping the temperature for 11min, finally cooling and reducing the pressure, taking out pyrophyllite blocks and cracking the pyrophyllite blocks to obtain the cubic boron nitride single crystal synthetic column.
(3) Crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain powdery cubic boron nitride crystals; preparing mixed acid of concentrated sulfuric acid with the mass concentration of 95% and concentrated nitric acid with the mass concentration of 64% according to the volume ratio of 4: 1; putting the powdery cubic boron nitride crystal crude product into the mixed acid, heating to 160 ℃, boiling for 5 hours, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in a sodium hydroxide solution with the mass concentration of 98%, heating to 250 ℃, boiling for 3 hours, repeatedly washing with water, and drying to obtain a cubic boron nitride crystal crude product; and screening the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with different particle sizes, such as 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-plus-120 meshes, 120-plus-140 meshes and the like. The granularity of the synthesized cubic boron nitride is mainly concentrated in 100-120 meshes, 120-140 meshes and a fine range, and the average yield of the cubic boron nitride with the granularity is about 60 percent.
Example 10:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) firstly, the required hexagonal boron nitride is treated for 2 hours at a high temperature of 200 ℃, and is treated in a vacuum oven in vacuum before use and is stored for use. 73kg of hexagonal boron nitride, 19kg of Mg-Al alloy powder and 8kg of feldspar powder are weighed by using a 0.1g precision electronic balance according to the mass percentage, wherein the weight ratio of the albite powder: potassium feldspar powder =1: 2. Firstly, adding 1/2 required hexagonal boron nitride into a three-dimensional mixer, then adding 7kg of Mg-Al alloy powder and 13kg of feldspar powder into the mixer, and finally adding the remaining 1/2 hexagonal boron nitride into the three-dimensional mixer, wherein the mixing time is 2.2 hours. And taking out the mixture after the material mixing is finished, carrying out vacuum packaging on the mixture by using a vacuum packaging machine, and carrying out grinding and pelleting under the pressure of 280MPa by using a cold isostatic press. Crushing the granules by a jaw crusher after granulation is finished, sieving the granules by a 80-mesh sieve to obtain granules for preparing the synthetic column, pressing the obtained granules into a synthetic rod by a full-automatic four-column oil press under the pressure of 12MPa, assembling the heating carbon tube and the heat-insulating ceramic sheet component into the synthetic rod, and storing the synthetic rod in a vacuum environment for later use before synthesis.
(2) The synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 46MPa at a boosting speed of 0.9MPa/s for 2min, then boosting the pressure to 77MPa at the same boosting speed at a time, heating when the pressure is raised to 36MPa in the boosting process, raising the temperature to 1700K within 4min, keeping the temperature for 8min, finally cooling and reducing the pressure, taking out pyrophyllite blocks and cracking to obtain the cubic boron nitride single crystal synthetic column.
(3) Crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain powdery cubic boron nitride crystals; preparing mixed acid of concentrated sulfuric acid with mass concentration of 96% and concentrated nitric acid with mass concentration of 65% according to the volume ratio of 4: 1; putting the powdery cubic boron nitride crystal crude product into the mixed acid, heating to 150 ℃, boiling for 5 hours, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in a sodium hydroxide solution with the mass concentration of 98%, heating to 270 ℃, boiling for 3 hours, repeatedly washing with water, and drying to obtain a cubic boron nitride crystal crude product; and screening the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with different particle sizes, such as 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-plus-120 meshes, 120-plus-140 meshes and the like. The synthesized cubic boron nitride particle size is mainly concentrated in 80-100 meshes, 100-120 meshes, 120-140 meshes and fine range, and the average yield of the cubic boron nitride with the particle size is about 56%.
Example 11:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) firstly, the required hexagonal boron nitride is treated for 2 hours at a high temperature of 200 ℃, and is treated in a vacuum oven in vacuum before use and is stored for use. Weighing 65kg of hexagonal boron nitride, 32kg of Mg-Al alloy powder and 3kg of feldspar powder by using a 0.1g precision electronic balance according to the mass percentage, wherein the weight ratio of the albite powder: potassium feldspar powder =1: 2. Firstly, adding 1/2 required hexagonal boron nitride into a three-dimensional mixer, then adding 7kg of Mg-Al alloy powder and 13kg of feldspar powder into the mixer, and finally adding the remaining 1/2 hexagonal boron nitride into the three-dimensional mixer, wherein the mixing time is 2.5 hours. And taking out the mixture after the material mixing is finished, carrying out vacuum packaging on the mixture by using a vacuum packaging machine, and carrying out grinding and pelleting under the pressure of 230MPa by using a cold isostatic press. Crushing the granules by a jaw crusher after granulation is finished, sieving the granules by a 80-mesh sieve to obtain granules for preparing the synthetic column, pressing the obtained granules into a synthetic rod by a full-automatic four-column oil press under the pressure of 16MPa, assembling the heating carbon tube and the heat-insulating ceramic sheet component into the synthetic rod, and storing the synthetic rod in a vacuum environment for later use before synthesis.
(2) The synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 49MPa at one time at a boosting speed of 0.85MPa/s, maintaining the pressure for 2min, then boosting the pressure to 76MPa at one time at the same boosting speed, starting heating when the pressure is raised to 35MPa in the boosting process, raising the temperature to 1600K within 3min, keeping the temperature for 10min, finally cooling and reducing the pressure, taking out pyrophyllite blocks and cracking the pyrophyllite blocks to obtain the cubic boron nitride single crystal synthesis column.
(3) Crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain powdery cubic boron nitride crystals; preparing mixed acid of concentrated sulfuric acid with the mass concentration of 97% and concentrated nitric acid with the mass concentration of 63% according to the volume ratio of 4: 1; putting the powdery cubic boron nitride crystal crude product into the mixed acid, heating to 170 ℃, boiling for 6 hours, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in 97% sodium hydroxide solution, heating to 200 ℃, boiling for 2h, repeatedly washing with water, and drying to obtain cubic boron nitride crystal crude product; and screening the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with different particle sizes, such as 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-plus-120 meshes, 120-plus-140 meshes and the like. The synthesized cubic boron nitride particle size is mainly concentrated in 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-120 meshes, 120-140 meshes and in a fine range, and the average yield of the particle size cubic boron nitride is about 45%.
Example 12:
a method for preparing a cubic boron nitride single crystal, comprising the steps of:
(1) firstly, the required hexagonal boron nitride is treated for 2 hours at a high temperature of 200 ℃, and is treated in a vacuum oven in vacuum before use and is stored for use. According to the mass percentage, 69kg of hexagonal boron nitride, 25kg of Mg-Al alloy powder and 6kg of feldspar powder are weighed by a 0.1g precision electronic balance, wherein the weight ratio of the albite powder: potassium feldspar powder =1: 2. Firstly, adding 1/2 required hexagonal boron nitride into a three-dimensional mixer, then adding 7kg of Mg-Al alloy powder and 13kg of feldspar powder into the mixer, and finally adding the remaining 1/2 hexagonal boron nitride into the three-dimensional mixer, wherein the mixing time is 2.2 hours. And taking out the mixture after the material mixing is finished, carrying out vacuum packaging on the mixture by using a vacuum packaging machine, and carrying out grinding and pelleting under the pressure of 280MPa by using a cold isostatic press. Crushing the granules by a jaw crusher after granulation is finished, sieving the granules by a 80-mesh sieve to obtain granules for preparing the synthetic column, pressing the obtained granules into a synthetic rod by a full-automatic four-column oil press under the pressure of 12MPa, assembling the heating carbon tube and the heat-insulating ceramic sheet component into the synthetic rod, and storing the synthetic rod in a vacuum environment for later use before synthesis.
(2) The synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 48MPa at a boosting speed of 0.95MPa/s for 2min, then boosting the pressure to 79MPa at the same boosting speed at a time, heating when the pressure is raised to 38MPa in the boosting process, raising the temperature to 1800K within 3min, keeping the temperature for 10min, finally cooling and reducing the pressure, taking out pyrophyllite blocks and cracking to obtain the cubic boron nitride single crystal synthetic column.
(3) Crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain powdery cubic boron nitride crystals; preparing mixed acid of concentrated sulfuric acid with the mass concentration of 97% and concentrated nitric acid with the mass concentration of 63% according to the volume ratio of 4: 1; putting the powdery cubic boron nitride crystal crude product into the mixed acid, heating to 150 ℃, boiling for 5 hours, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in 97% sodium hydroxide solution, heating to 230 ℃, boiling for 2h, repeatedly washing with water, and drying to obtain cubic boron nitride crystal crude product; and screening the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with different particle sizes, such as 60-70 meshes, 70-80 meshes, 80-100 meshes, 100-plus-120 meshes, 120-plus-140 meshes and the like. The synthesized cubic boron nitride particle size is mainly concentrated in 70-80 meshes, 80-100 meshes, 100-120 meshes, 120-140 meshes and in a fine range, and the average yield of the cubic boron nitride with the particle size is about 50%.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the overall concept of the present invention, and these should also be considered as the protection scope of the present invention.
Claims (6)
1. A method for preparing a cubic boron nitride single crystal is characterized by comprising the following steps: the method comprises the following steps:
(1) weighing 60-85 parts of hexagonal boron nitride powder, 5-35 parts of Mg-Al alloy powder and 1-15 parts of feldspar powder according to the mass parts, uniformly mixing, and pressing into a synthetic column;
(2) applying synthesis pressure of 75-80MPa to the synthesis column obtained in the step (1) at 1600-1800k for high-temperature high-pressure synthesis to obtain a black cubic boron nitride crystal crude product;
(3) crushing the obtained cubic boron nitride crystal crude product to obtain a blocky cubic boron nitride crystal crude product, and performing acid treatment, alkali treatment, drying and screening on the blocky cubic boron nitride crystal crude product to obtain a cubic boron nitride crystal finished product; the granularity range of the obtained cubic boron nitride crystal finished product is 60-140 meshes;
the feldspar powder in the step (1) consists of albite powder and potassium feldspar powder, and the mass ratio of the albite powder to the potassium feldspar powder is 1:4-1: 2.
2. The method of producing a cubic boron nitride single crystal according to claim 1, characterized in that: the step (1) is specifically as follows: weighing the raw materials in parts by weight, adding 50% of hexagonal boron nitride powder into a mixer, adding Mg-Al alloy powder and feldspar powder into the mixer, and adding the rest hexagonal boron nitride powder into the mixer to be uniformly mixed; vacuum packaging the obtained mixed powder, extruding and granulating under 200-300 MPa by using a cold isostatic press, crushing by using a jaw crusher after granulation is finished, screening by using an 80-mesh screen to obtain granules for preparing the synthetic column, and pressing the obtained granules into the synthetic column under 10-20MPa by using a full-automatic oil press; the synthetic column, the heating carbon tube and the heat-insulating ceramic sheet component are assembled into a synthetic rod, and the synthetic rod is stored in a vacuum environment for standby before synthesis.
3. The method of producing a cubic boron nitride single crystal according to claim 1, characterized in that: the hexagonal boron nitride powder is subjected to high-temperature treatment at 200 ℃ for 2 hours before use, is subjected to heat preservation at 120 ℃ for standby, and is dried in vacuum before use.
4. The method of producing a cubic boron nitride single crystal according to claim 1, characterized in that: the step (2) is specifically as follows: the synthesis column group is arranged in a pyrophyllite block, and a hinge beam type cubic top press is used for generating high-temperature and high-pressure conditions to synthesize cubic boron nitride single crystals; the method specifically comprises the following steps: firstly, boosting the pressure to 45-50MPa at a boosting speed of 0.8-1.2MPa/s for one time, maintaining the pressure for 2min, then boosting the pressure to 75-80MPa at the same boosting speed at one time, starting heating when the pressure is raised to 35-38MPa in the boosting process, raising the temperature to 1600-1800K within 2-4min, keeping the temperature for 8-15min, finally, reducing the temperature and the pressure, taking out pyrophyllite blocks and cracking to obtain the cubic boron nitride single crystal synthesis column.
5. The method of producing a cubic boron nitride single crystal according to claim 1, characterized in that: the step (3) is specifically as follows: crushing and ball-milling the cubic boron nitride crude product by using a jaw crusher and a ball mill to obtain powdery cubic boron nitride crystal crude product; preparing mixed acid of concentrated sulfuric acid with the mass concentration of 95-98% and concentrated nitric acid with the mass concentration of 63-65% according to the volume ratio of 4: 1; placing the powdery cubic boron nitride crystal crude product in the mixed acid, heating to 150 ℃ and 180 ℃, boiling for 4-6h, repeatedly washing with water and drying to obtain granular cubic boron nitride crystal crude product; placing the cubic boron nitride crystal crude product in a sodium hydroxide solution with the mass concentration of 95-98%, heating to 180-280 ℃, boiling for 2-3h, repeatedly washing with water and drying to obtain the cubic boron nitride crystal crude product; and sequentially sorting the cubic boron nitride crystal crude product by using an ultrasonic-assisted rotary vibration sieve to obtain cubic boron nitride crystals with different particle sizes.
6. The method of producing a cubic boron nitride single crystal according to claim 5, characterized in that: crushing and ball-milling the cubic boron nitride crystal crude product by using a jaw crusher and a ball mill to obtain powdery cubic boron nitride crystal crude product specifically: crushing the whole synthetic rod into blocky particles with the particle size smaller than 12 meshes by using a jaw crusher, soaking the blocky particles by using hot water and continuously stirring until no bubbles are generated, then carrying out ball milling on the blocky particles by using a ball mill, and drying to obtain the powdery cubic boron nitride crystal.
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