Method for preparing high-purity cbn micropowder

Abstract

The present application relates to a high-purity CBN micro-powder preparation method, which comprises the following steps: mixing dehydrated borax with urea, heating and reacting in an ammonia gas flow, and obtaining boron nitride after purifying the reaction product; mixing a catalyst, HBN material and a catalytic additive; sealing, static pressing, granulating, pressing into a synthesis column, assembling into a synthetic block with a block mechanism, loading the synthetic block into a six-surface pressing machine, knocking the high-pressure synthetic block sample obtained by high-temperature and high-pressure synthesis into pieces, loading the pieces into a ball mill tank, opening the ball mill tank after ball milling, adding deionized water for boiling, collecting CBN at the bottom of the container, boiling in a strong alkali solution, and then washing with deionized water; collecting CBN at the bottom of the container, boiling in a strong acid solution, and then washing with deionized water, drying, shaping, screening and selecting, to obtain CBN crystal micro-powder; the present application has the advantages of high purity, good thermal stability, high grinding efficiency, high purity, high wear resistance, high thermal stability, etc.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of CBN and particularly relates to a high-purity CBN micro-powder preparation method. BACKGROUND

[0002] Cubic boron nitride and products are widely used in the departments of automobile, machinery, electronics, aviation, aerospace, optical instruments, glass, ceramics, petroleum and geology. With the continuous development of technology and products, diamond micro-powder and products have been fully developed in the application in the fields of 3C, SiC semiconductor processing and photovoltaic. In the prior art, the industrial production of CBN single crystal micro-powder is mainly to synthesize CBN single crystal abrasive particles, then to crush and shape the particles, and to produce the particles by using a special process. The CBN single crystal abrasive particles synthesized by the prior method use active noble metals as catalyst materials, and it is difficult to store and synthesize nitrides, the cost is high, the process flow is complex, and the produced products have high impurity content and low strength. The conversion rate of the prior method is low, about 30-40%, the crystal particle size is large, and the particle size is about 100 mesh, which is not suitable for industrial batch production of single crystal micro-powder. Therefore, it is necessary to provide a high-purity CBN micro-powder preparation method with high purity, high grinding efficiency, high wear resistance and high thermal stability. SUMMARY

[0003] The application aims to overcome the shortcomings of the prior art and provide a high-purity CBN micro-powder preparation method with high purity, high wear resistance and high thermal stability.

[0004] The application is achieved in the following manner. The high-purity CBN micro-powder preparation method comprises the following steps:

[0005] Step 1: mix dehydrated borax with urea, heat and react in an ammonia gas flow, purify the reaction product to obtain boron nitride;

[0006] Step 2: mix 200-mesh anhydrous borax with urea at a molar ratio of 1:2.3-2.5 to generate an intermediate of borax and urea;

[0007] Step 3: cool and crush the intermediate to 300-350 mesh, press into blocks on a press with a mold, and then send into a nitriding furnace to react in an ammonia gas flow for about 6-8 h; then stop heating, pass in ammonia, and stop passing in ammonia when the furnace temperature cools to below 300-400℃, and continue to cool to an appropriate temperature;

[0008] Step 4: take out the boron nitride crude product, crush to 200 mesh, soak in dilute acid for two times, each time for about 12-15 h, then wash with deionized water until neutral, filter, dry, crush, and obtain boron nitride products with a purity of 95%-98%.

[0009] Step 5: According to the weight ratio, 2-15 parts of catalyst, 80-93 parts of HBN material and 0.2-4.5 parts of catalytic additive are mixed on a three-dimensional mixer for 10 hours;

[0010] Step 6: The mixed material is sealed and subjected to static pressure and granulation, and then pressed into a synthetic column of a certain size. The synthetic column is loaded into a vacuum reduction furnace for reduction by using a stepwise reduction process. The reduction temperature ranges from 1150 to 1200°C, and the reduction time is not less than 6 hours. The reduced synthetic column is vacuum packaged for use;

[0011] Step 7: The synthetic column formed in the previous step is loaded into a leaf talc block mechanism to form a synthetic block, which is then loaded into the high-pressure chamber of a six-surface press and pressurized to 3-7 GPa. The temperature is heated to 1200-1400°C, and the duration is 4-8 hours. The high-pressure synthetic block sample is obtained;

[0012] Step 8: The high-pressure synthetic block sample obtained by high-temperature and high-pressure synthesis is crushed by knocking, and then the crushed material is placed in a ball mill tank and a certain amount of ball milling medium and dry ball milling reagent are added, and the tank is covered;

[0013] Step 9: The ball mill tank is placed in the ball mill, and the rotation speed is adjusted to 400 rpm. The rotation time is 10 hours, and the rotation is alternately operated;

[0014] Step 10: After the ball mill stops working, the ball mill tank is opened. The mixture in the ball mill tank is completely caked and attached to the tank wall. A certain amount of deionized water is added to wet the mixture in the ball mill tank. The mixture is softened and dispersed in the deionized water. The pH is measured to be about 8. After 2 hours of water bath ultrasonic treatment, the liquid mixture is transferred to a dialysis belt for dialysis to remove urea. After a period of water bath dialysis at 35°C, centrifugal treatment is performed at 3000 rpm for 30 minutes;

[0015] Step 11: Since the CBN single crystal has a high density, it is precipitated at the bottom of the container. The solution in the container is filtered out, and water boiling is performed with deionized water for 4-6 times to remove most of the cubic boron nitride powder;

[0016] Step 12: Then the CBN collected at the bottom of the container is boiled in a strong alkali solution for 20-30 minutes, and then washed with deionized water to remove residual cubic boron nitride powder. The CBN collected at the bottom of the container is then boiled in a strong acid solution for 20-30 minutes, and then repeatedly washed with deionized water to remove residual metal impurities;

[0017] Step 13: The obtained CBN is then dried in an oven at 110-140℃ for 8h, and the pure CBN is shaped, screened and selected to obtain CBN crystal powder.

[0018] The reaction formula of step 1 is: Na2B4O7+2(NH2)2CO→4BN+Na2O+4H2O+2CO2.

[0019] The specific step of step 2 is: 200 mesh anhydrous borax is mixed with urea at a molar ratio of 1:2.3-2.5. Since urea contains a small amount of free water, it is very easy to form blocks and not easy to mix. Therefore, it needs to be dried at 100℃ before mixing, and then crushed to 200 mesh. The mixed material is then placed in a reactor at a temperature of 200-400℃ for condensation reaction for about 3-5h to generate borax and urea intermediates.

[0020] The temperature condition for the reaction in step 3 is 800-1050℃ or 1000-1200℃.

[0021] The catalyst in step 5 is one of alkali metal, alkaline earth metal and its nitride catalyst, aluminum-based alloy catalyst, and water catalyst.

[0022] The alkali metal, alkaline earth metal and its nitride catalyst is Ca3B2N4; the aluminum-based alloy catalyst is one of Al-Si, Al-Ni, Al-Cr, Al-Mn and Al-Co.

[0023] The catalytic additive in step 5 is one or more of Al, La and B4C, and the purity of each is above 99.99%.

[0024] The ball milling medium in step 8 is zirconia ball, and the dry ball milling agent is urea.

[0025] The ball mill in step 9 is a planetary ball mill for mechanical ball milling.

[0026] The alkali treatment of cubic boron nitride and pyrophyllite in step 12 is: low-temperature molten K and Na metal hydroxide can dissolve cubic boron nitride without affecting CBN; to prevent CBN corrosion at high temperature, a mixed alkali of NaOH: KOH=1:2 by mass can be used to reduce the melting point; after alkali treatment, the dissolved substances are washed away with deionized water, and then acid washed to neutral, to obtain CBN.

[0027] The application has the advantages that: the application is a high-purity CBN micro-powder preparation method, in which high-quality catalyst is used to meet the kinetic condition, and the catalyst in a molten state is dissolved in HBN under stable high temperature to meet the stable thermodynamic condition, i.e., stable P-T condition, and then CBN crystals are precipitated, and the crystal nucleus gradually grows under appropriate high temperature and high pressure condition; the purification process of the method can effectively remove most of the cubic boron nitride powder, and then remove the residual cubic boron nitride powder through alkali treatment, and remove the residual metal impurities through acid treatment, so that more pure cubic boron nitride micro-powder is obtained, i.e., the purity of the boron nitride product is 95%-98%; the CBN prepared by the method is black cubic boron nitride micro-powder, which is commonly used in resin binder system, abrasive oil stone, etc.; the method has high CBN conversion rate, fine particle size, and a yield of about 45%, simplifies the production process of CBN single crystal micro-powder, reduces the synthesis cost and synthesis pressure condition, and has good economic and social benefits; the CBN micro-powder product prepared by the method has high purity, high wear resistance, and high thermal stability, and is used for the production of PCBN composite sheet and polycrystalline sintered body with longer service life; the application has the advantages of high purity, high wear resistance, and high thermal stability. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 SED of the application Figure 1 .

[0029] Figure 2 SED of the application Figure 2 .

[0030] Figure 3 SED of the application Figure 3 .

[0031] Figure 4 SED of the application Figure 4 . DETAILED DESCRIPTION

[0032] The application will be further described below with reference to the drawings.

[0033] Example 1

[0034] As shown in the drawings, the high-purity CBN micro-powder preparation method comprises the following steps: Figures 1-4 Step 1: mix the dehydrated borax with urea, heat and react in an ammonia gas flow, purify the product obtained by the reaction to obtain boron nitride;

[0035] Step 2: mix 200-mesh anhydrous borax with urea at a molar ratio of 1:2.3 to generate an intermediate of borax and urea;

[0036] Step 2: mix 200-mesh anhydrous borax with urea at a molar ratio of 1:2.3 to generate an intermediate of borax and urea;

[0037] Step 3: After the intermediate is cooled, it is crushed to 300 mesh, pressed into a block on a press with a mold, and then sent to a nitriding furnace to react in an ammonia stream for about 6 hours; after that, the heating is stopped, ammonia is introduced, and the furnace temperature is cooled to below 300°C to stop the ammonia flow, and then cooled to an appropriate temperature;

[0038] Step 4: The crude boron nitride is removed, crushed to 200 mesh, and then soaked in dilute acid for about 12 hours twice, and then washed with deionized water until neutral, filtered, dried, and crushed to obtain a 95% pure boron nitride product;

[0039] Step 5: According to the weight ratio, 2 parts of catalyst, 80 parts of HBN material, and 0.2 parts of catalytic additive are mixed on a three-dimensional mixer for 10 hours;

[0040] Step 6: The mixed material from the previous step is sealed and subjected to static pressure and granulation, and then pressed into a synthetic column of a certain size. The synthetic column is loaded into a vacuum reduction furnace and subjected to a stepwise reduction process. The reduction temperature range is 1150°C, and the reduction time is not less than 6 hours. The reduced synthetic column is vacuum packaged for use;

[0041] Step 7: The synthetic column formed in the previous step is loaded into a leaf talc block mechanism to form a synthetic block, which is then loaded into the high-pressure chamber of a six-surface press and pressurized to 3GPa. The temperature is heated to 1200°C, and the duration is 4 hours. The high-pressure synthetic block sample is obtained;

[0042] Step 8: The high-pressure synthetic block sample obtained by high-temperature and high-pressure synthesis is crushed, and then the crushed material is placed in a ball mill tank and a certain amount of ball milling medium and dry ball milling agent is added, and the tank is covered;

[0043] Step 9: Place the ball mill tank in the ball mill and adjust the rotation speed to 400 rpm. Rotate for 10 hours with alternating operation;

[0044] Step 10: After the ball mill stops working, open the ball mill tank. The mixture in the tank is clumped and attached to the tank wall. Add deionized water to wet the mixture in the tank. The mixture softens and disperses in the deionized water. Measure the pH with pH paper, which is about 8. After 2 hours of ultrasonic treatment in a water bath, transfer the liquid mixture to a dialysis belt to remove urea. After dialysis for a period of time in a 35°C water bath, centrifuge at 3000 rpm for 30 minutes;

[0045] Step 11: Since the CBN single crystal has a high density, it is precipitated at the bottom of the container. The solution in the container is filtered and then boiled in deionized water for 4 times to remove most of the cubic boron nitride powder;

[0046] Step 12: then the CBN collected at the bottom of the container is put into a strong alkali solution and boiled for 20 min, and then washed with deionized water to remove residual cubic boron nitride powder; then the CBN collected at the bottom of the container is put into a strong acid solution and boiled for 20 min, and then repeatedly washed with deionized water to remove residual metal impurities;

[0047] Step 13: then the obtained CBN is put into an oven at 110℃ and dried for 8h, and the pure CBN is shaped, and after shaping, screening and shaping selection are performed, so that CBN crystal micro powder is obtained.

[0048] In this embodiment, in order to further illustrate the performance of the present application, the following provides specific effect data; the impurity content of the sample is determined by ICP method and nitrogen oxygen analysis method, and the specific surface area and particle size composition of the sample are determined by specific surface area tester and laser particle size analyzer, and the component composition and physical properties of the HBN prepared by the preparation method of the present application are shown in Table 1 and Table 2.

[0049] Table 1 Component composition of HBN prepared by borax and urea method

[0050]

[0051] Table 2 Physical properties of HBN prepared by borax and urea method

[0052]

[0053] The present application is a preparation method of high-purity CBN micro powder. In use, the catalyst of the present application uses high-quality catalyst, meets the kinetic condition, meets the stable thermodynamic condition, i.e. stable P-T condition, at a stable high temperature, the catalyst in a molten state dissolves HBN, and then CBN crystals are precipitated, and the crystal nucleus gradually grows under appropriate high temperature and high pressure conditions. The purification process of the method of the present application can effectively remove most of the cubic boron nitride powder; and the residual cubic boron nitride powder is removed by alkali treatment, and the residual metal impurities are removed by acid treatment, so that more pure cubic boron nitride micro powder is obtained, i.e. boron nitride product with a purity of 95%-98%; the CBN prepared by the method of the present application is black cubic boron nitride micro powder, which is commonly used in resin binder system, abrasive oil stone, etc.; the preparation method of the present application has high CBN conversion rate, fine particle size, and a yield of about 45%, simplifies the production process of CBN single crystal micro powder, reduces the synthesis cost and synthesis pressure condition, and has good economic and social benefits; the CBN micro powder product prepared by the method of the present application has high purity, high wear resistance and high thermal stability, and is used for the production of PCBN composite sheet and polycrystalline sintered body with longer service life; the present application has the advantages of high purity, high wear resistance and high thermal stability.

[0054] Example 2

[0055] AsFigures 1-4 A high-purity CBN powder preparation method is shown, the method comprising the following steps:

[0056] Step 1: After dehydration, the borax is mixed with urea, heated in an ammonia stream, and the product is purified to obtain boron nitride;

[0057] Step 2: 200 mesh anhydrous borax is mixed with urea in a molar ratio of 1:2.4 to form an intermediate of borax and urea;

[0058] Step 3: The intermediate is cooled and crushed to 325 mesh, pressed into a block on a press with a mold, and then sent to a nitriding furnace for reaction in an ammonia stream for about 7 hours; then stop heating, pass ammonia, stop passing ammonia when the furnace temperature cools to below 350°C, and continue cooling to an appropriate temperature;

[0059] Step 4: The crude boron nitride is removed, crushed to 200 mesh, and then soaked in dilute acid for about 13 hours each time, then washed with deionized water to neutral, filtered, dried, and crushed to obtain boron nitride products with a purity of 96.5%;

[0060] Step 5: According to the weight ratio, 8.5 parts of catalyst, 8.65 parts of HBN material and 2.3 parts of catalytic additive are mixed on a three-dimensional mixer for 10 hours;

[0061] Step 6: The mixed material is sealed and granulated by static pressure, and then pressed into a certain size synthesis column. The synthesis column is loaded into a vacuum reduction furnace and subjected to a stepwise reduction process. The reduction temperature range is 1175°C, and the reduction time is not less than 6 hours. The reduced synthesis column is vacuum packaged for use;

[0062] Step 7: The synthesis column formed in the previous step is loaded into a leaf talc block mechanism to form a synthesis block, and then the synthesis block is loaded into the high-pressure cavity of a six-surface press, pressurized to 5GPa, and heated to 1300°C for 6 hours to obtain a high-pressure synthesis block sample;

[0063] Step 8: The high-pressure synthesis block sample obtained by high-temperature and high-pressure synthesis is crushed, and then the crushed material is placed in a ball mill tank and a certain amount of ball milling medium and dry ball milling reagent is added, and the cover is closed;

[0064] Step 9: Place the ball mill tank in the ball mill, adjust the rotation speed to 400 rpm, and rotate for 10 hours, alternating operation;

[0065] Step 10: After the ball mill stops working, open the ball mill tank, the mixture in the ball mill tank is clumped and attached to the tank wall as a whole, add some deionized water to wet the mixture in the ball mill tank, the mixture is softened and dispersed in the deionized water, measure the pH value of the mixture by using pH test paper, the pH value is about 8, after ultrasonic treatment for 2 hours in water bath, transfer the liquid mixture to the dialysis belt to remove urea by dialysis, after dialysis for a period of time in 35℃ water bath, centrifugal treatment at 3000 rpm for 30 minutes;

[0066] Step 11: Since the density of CBN single crystal is large, the precipitate is at the bottom of the container, filter out the solution in the container, and then perform water boiling with deionized water for 5 times to remove most of the cubic boron nitride powder;

[0067] Step 12: Then collect the CBN at the bottom of the container and boil it in a strong alkali solution for 25 minutes, then rinse it with deionized water to remove the residual cubic boron nitride powder; then collect the CBN at the bottom of the container and boil it in a strong acid solution for 25 minutes, then rinse it repeatedly with deionized water to remove the residual metal impurities;

[0068] Step 13: Then put the obtained CBN into an oven at 125℃ for 8h, shape the pure CBN, and then screen and select the shape to obtain CBN crystal micro powder.

[0069] The high-purity CBN micro powder preparation method of the present application uses high-quality catalysts to meet the kinetic conditions and stable thermodynamic conditions (i.e. stable P-T conditions) at stable high temperatures, the catalyst in a molten state dissolves HBN, and then CBN crystals are precipitated, and the crystal nucleus gradually grows under appropriate high temperature and high pressure conditions; the purification process of the method can effectively remove most of the cubic boron nitride powder, and then remove the residual cubic boron nitride powder by alkali treatment, and then remove the residual metal impurities by acid treatment, so as to obtain more pure cubic boron nitride micro powder, i.e. boron nitride products with a purity of 95%-98%; the CBN prepared by the method of the present application is black cubic boron nitride micro powder, which is commonly used in resin binder systems, abrasive oil stones, etc.; the preparation method of the present application has high CBN conversion rate, fine particle size, and a yield of about 45%, which simplifies the production process of CBN single crystal micro powder, reduces the synthesis cost and synthesis pressure conditions, and has good economic and social benefits; the CBN micro powder product prepared by the method of the present application has high purity, high wear resistance, and high thermal stability, and is used for the production of PCBN composite sheets and polycrystalline sintered bodies with longer service life; the present application has the advantages of high purity, high wear resistance, and high thermal stability.

[0070] Example 3

[0071] As shown in Figures 1-4 The method comprises the following steps:

[0072] Step 1: mix the dehydrated borax with urea, heat the reaction in the ammonia stream, and purify the product to obtain boron nitride;

[0073] Step 2: mix 200 mesh anhydrous borax with urea in a 1:2.5 molar ratio to form an intermediate of borax and urea;

[0074] Step 3: crush the intermediate to 350 mesh after cooling, press it into a block on a press with a mold, and then put it into a nitriding furnace to react in the ammonia stream for about 8 hours; then stop heating, pass in ammonia, and wait for the furnace temperature to cool to below 400°C to stop passing in ammonia, and continue cooling to an appropriate temperature;

[0075] Step 4: take out the crude boron nitride, crush it to 200 mesh, then soak it in dilute acid for about 15 hours each time, then wash it with deionized water to neutralize it, filter, dry, and crush to obtain a 98% pure boron nitride product;

[0076] Step 5: mix 15 parts of catalyst, 93 parts of HBN material, and 4.5 parts of catalytic additive in a three-dimensional mixer for 10 hours according to the weight ratio;

[0077] Step 6: seal the mixed material from the previous step, press it, granulate it, and press it into a synthetic column of a certain size, put the synthetic column into a vacuum reduction furnace, and use a step-by-step reduction process to reduce it, with a reduction temperature range of 1200°C and a reduction time of not less than 6 hours, and then vacuum package the reduced synthetic column for use;

[0078] Step 7: put the synthetic column formed in the previous step into a leaf talc block mechanism to form a synthetic block, then put the synthetic block into the high-pressure chamber of a six-surface press, press it to 7 GPa, heat it to 1400°C, and continue for 8 hours to obtain a high-pressure synthetic block sample;

[0079] Step 8: knock the high-temperature high-pressure synthetic block sample obtained in the previous step into pieces, then put the crushed material into a ball mill jar, and add a certain amount of ball milling medium and dry ball milling reagent, and cover the lid;

[0080] Step 9: place the ball mill jar in the ball mill, adjust the rotation speed to 400 rpm, and rotate for 10 hours, alternating between running and stopping;

[0081] Step 10: after the ball mill stops working, open the ball mill jar, add deionized water to the mixture in the ball mill jar, and then measure the pH of the mixture to be about 8, then ultrasonic the mixture in the water bath for 2 hours, then transfer the liquid mixture to a dialysis belt to remove the urea, and then centrifuge the mixture at 3000 rpm for 30 minutes.

[0082] Step 11: Since the CBN single crystal has a large density, it is precipitated at the bottom of the container, the solution in the container is filtered out, and water boiling is carried out after deionized water, which is repeated 6 times to remove most of the cubic boron nitride powder;

[0083] Step 12: Then the CBN at the bottom of the container is collected and boiled in a strong alkali solution for 30 min, then washed with deionized water to remove residual cubic boron nitride powder; then the CBN at the bottom of the container is collected and boiled in a strong acid solution for 30 min, then repeatedly washed with deionized water to remove residual metal impurities;

[0084] Step 13: Then the obtained CBN is placed in an oven at 140°C and dried for 8h, and the pure CBN is shaped, and after shaping, screening and shape selection are carried out to obtain CBN crystal micro powder.

[0085] In this embodiment, in order to further illustrate the performance of the present application, the following provides specific effect data; in order to further quantify the characteristics of CBN micro powder, CBN micro powder is selected, and its structure is characterized in detail by using a scanning electron microscope, and the results are shown in Figures 1-4 ; magnetic susceptibility: the magnetic susceptibility of the CBN micro powder is measured by using a JCC-B type magnetic susceptibility tester, 6 batches of ordinary CBN micro powder and CBN micro powder of the present application are selected, and the average value of the magnetic susceptibility is calculated, as shown in Table 3;

[0086] Table 32 CBN magnetic susceptibility comparison

[0087]

[0088]

[0089] From the magnetic susceptibility determination results in Table 3, the average value of the magnetic susceptibility of the CBN of the present application is reduced by 1.8x10 -5 SI, with a reduction of more than 65%, which is much lower than that of ordinary CBN; the magnetic susceptibility of CBN is caused by internal metal impurities, the more such impurities, the stronger the magnetism of CBN; which shows that the internal impurities of the CBN of the present application are much less than those of ordinary CBN; the CBN prepared by the preparation method of the present application is black cubic boron nitride micro powder, with high crystal purity, good thermal stability, good self-sharpening, high grinding efficiency and other characteristics.

[0090] The application is a high-purity CBN micro-powder preparation method. In use, the catalyst of the application adopts high-quality catalyst, meets the kinetic condition, meets the stable thermodynamic condition, i.e. stable P-T condition, at a stable high temperature, the catalyst in a molten state dissolves HBN, and then CBN crystals are precipitated, and the crystal nucleus gradually grows under appropriate high temperature and high pressure conditions. The purification process of the method can effectively remove most cubic boron nitride powder, and remove the residual cubic boron nitride powder through alkali treatment, and remove the residual metal impurities through acid treatment, so as to obtain more pure cubic boron nitride micro-powder, i.e. a boron nitride product with a purity of 95%-98%. The CBN prepared by the method is black cubic boron nitride micro-powder, and is commonly used in resin binder systems, abrasive oil stones, etc. The preparation method has high CBN conversion rate, fine particle size, and a yield of about 45%, simplifies the production process of CBN single crystal micro-powder, reduces the synthesis cost and synthesis pressure condition, and has good economic and social benefits. The CBN micro-powder product prepared by the method has high purity, high wear resistance, and high thermal stability, and is used in the production of long-service-life PCBN composite sheets and polycrystalline sintered bodies. The application has the advantages of high purity, high wear resistance, and high thermal stability.

Claims

1. A method for preparing high-purity CBN micro powder, characterized in that: The method includes the following steps: Step 1: Mix 200-mesh anhydrous borax and dried urea at a molar ratio of 1:2.3~2.

5. Allow the mixture to undergo a condensation reaction for 2-4 hours to generate an intermediate between borax and urea. Step 2: After cooling the intermediate to 60°C, crush it, then put it into an 80-mesh sieve in a nitriding furnace and flow it in a nitriding liquid at 800-950°C for 2-4 hours. After the reaction, the product is cooled in an ammonia atmosphere and then acid-washed, washed and dried to obtain a rapid boron nitride (BN) product. Step 3: Mix 2-15 parts of catalyst, 80-93 parts of B4C, 56-65 parts of BN powder, and 0.2-4.5 parts of catalytic additive in a three-dimensional mixer for 10 hours according to the weight ratio. Step 4: Place the mixed powder from the previous step into a high-temperature furnace and heat it at a high temperature; Step 5: Place the mixed powder material formed in the previous step into a reactor, introduce nitrogen- and boron-containing gases, and carry out a chemical reaction under certain temperature and pressure. B4C and BN react to generate CBN micro powder; control the heat treatment time and temperature to obtain the desired CBN micro powder size and shape. Step 6: After cooling, put the prepared CBN micro powder into a ball mill jar, place the ball mill jar in a ball mill, adjust the speed to 400 rpm, and rotate for 10 hours, alternating between the two. Step 7: After the ball mill stops working, open the ball mill jar, add a certain amount of deionized water to wet the mixture in the ball mill jar, soften and disperse the mixture in the deionized water, sonicate the mixture in a water bath for 2 hours, transfer the liquid mixture to the dialysis belt to remove urea, dialyze in a 35°C water bath for a period of time, and then centrifuge at 3000 rpm for 30 minutes. Step 8: Due to the high density of CBN single crystals, the precipitate will settle at the bottom of the container. Filter out the solution in the container, use deionized water, and boil it in water. Repeat this process 4-6 times to remove most of the cubic boron nitride powder. Step 9: Then, place the obtained CBN in an oven at 110-140℃ and dry it for 8 hours. The dried powder is then sieved and finely processed to remove impurities and unacceptable particles, thereby obtaining CBN crystal micro powder. The catalyst used in step 3 is one of alkali metal, alkaline earth metal and their nitride catalysts, aluminum-based alloy catalysts, and water catalysts. The catalytic additive in step 3 is one or more of Al, La, and B4C, and its purity is above 99.99%.

2. The method for preparing high-purity CBN micro powder as described in claim 1, characterized in that: The reaction formula in step 1 is: Na2B4O7 + 2(NH2)2CO → 4BN + Na2O + 4H2O + 2CO2.

3. The method for preparing high-purity CBN micro powder as described in claim 1, characterized in that: The specific steps of step 2 are as follows: after crushing the crude boron nitride, it is soaked in dilute acid twice, each time for 12-15 hours, and then washed with deionized water multiple times until neutral. After filtration, drying and pulverization, a boron nitride product with a purity of 95%-98% is obtained.

4. The method for preparing high-purity CBN micro powder as described in claim 1, characterized in that: The B4C micro powder in step 3 is prepared by sol-gel method or co-precipitation method.

5. The method for preparing high-purity CBN micro powder as described in claim 1, characterized in that: The alkali metal, alkaline earth metal and their nitride catalysts are made of Ca3B2N4; the aluminum-based alloy catalysts are made of one of Al-Si, Al-Ni, Al-Cr, Al-Mn and Al-Co.

6. The method for preparing high-purity CBN micro powder as described in claim 1, characterized in that: The temperature range in step 4 is 1150-1200℃, and the time is not less than 6 hours.

7. The method for preparing high-purity CBN micro powder as described in claim 1, characterized in that: The chemical reaction temperature and pressure in step 5 are as follows: the temperature is heated to 1200-1400℃, the pressure is increased to 3-7GPa, and the duration is 4-8h.

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