CN111286713B - High-efficiency treatment method and device for diamond micro powder - Google Patents

Abstract

A high-efficiency treatment method and a device for diamond micropowder belong to the technical field of diamond processing. The method is that diamond micro powder preheated to 600-900 ℃ is placed on a deposition table in a cavity of a microwave plasma chemical vapor deposition system through a conveying and placing device under the vacuum condition. The method is characterized in that ultrasonic waves and negative bias voltage are applied for assistance while etching treatment is carried out at 600-900 ℃ by uninterrupted argon, hydrogen and oxygen mixed plasmas, so that mutual collision among diamond micro powder particles is realized, the diamond micro powder is promoted to be uniformly etched by the plasmas, irregular protrusions on the surfaces of the diamond particles and impurities such as non-diamond in the micro powder are fully eliminated, and the spherical pure diamond micro powder is obtained. And then the processed diamond micro powder is taken out under the vacuum condition through a conveying and taking-out device at the other side and is synchronously cooled. Meanwhile, the next batch of diamond micropowder is conveyed and the treatment process is repeated, so that the continuous high-efficiency treatment of pure and uniform spheroidal diamond micropowder particles is realized.

Description

High-efficiency treatment method and device for diamond micro powder

The technical field is as follows:

the invention relates to the field of diamond processing and technology, in particular to a method for conveying diamond micro powder preheated to 600-900 ℃ on a deposition table in a cavity of a microwave plasma chemical vapor deposition system by a conveying and placing device under a vacuum condition. The method is characterized in that ultrasonic waves and negative bias voltage are applied for assistance while etching treatment is carried out at 600-900 ℃ by uninterrupted argon, hydrogen and oxygen mixed plasmas, so that mutual collision among diamond micro powder particles is realized, the diamond micro powder is promoted to be uniformly etched by the plasmas, irregular protrusions on the surfaces of the diamond particles and impurities such as non-diamond in the micro powder are fully eliminated, and the spherical pure diamond micro powder is obtained. And then the processed diamond micro powder is taken out under the vacuum condition through a conveying and taking-out device at the other side and is synchronously cooled. Meanwhile, the next batch of diamond micropowder is conveyed and the treatment process is repeated, so that the continuous high-efficiency treatment of pure and uniform spheroidal diamond micropowder particles is realized.

Technical Field

The diamond micropowder not only has ultrahigh intrinsic hardness of diamond, but also has high strength and high toughness due to the reduction of defects accompanying the grain size refinement. Its dual advantages constitute its unique physical properties, and thus have important applications in high and new technology industries and the traditional strut industry in the fields of fine grinding, polishing, lubricants, wire cutting, etc. The method is mainly applied to the fields of chips, optical crystals, ultra-fine processing, ultra-precision polishing of large-size silicon wafers, surface modification and the like. In particular, with the development of advanced technology and high-end manufacturing, many precision devices, such as computer disks, magnetic heads, optical communication devices, optical crystals, semiconductor substrates, etc., require higher surface finish and more precise polishing. If the surface has any convex-concave, scratch or foreign matter outside the allowable range, the designed precision and performance can not be guaranteed. Diamond micropowder is used as a superhard fine grinding and polishing material in the world at present, and comprises micron, submicron and nanometer powder in terms of granularity. China accounts for more than 80% of the world diamond micro powder yield in research and development and production of diamond micro powder, but the quality problem of the diamond micro powder becomes an important development bottleneck. The quality of the diamond micropowder determines the application range and the performance indexes of related products. The quality factors of the grinding wheel mainly comprise granularity marks, granularity distribution range, granule appearance, impurity content and grinding performance. The detection of the diamond micro powder particle size distribution is to evaluate the quality level of the particle size classification, and the diamond micro powder particle size distribution is expected to have a narrow particle size distribution range, concentrated particle size and a prominent particle size peak value. The particle morphology of the diamond micropowder is an important index in the diamond thinning process, and the particle shape of the diamond micropowder is required to be similar to a sphere, while the number of flaky or rectangular particles is required to be less. Meanwhile, the impurity content is another important index for evaluating the diamond micropowder, and the use effect in subsequent engineering application is directly influenced. For example, diamond micro powder with the average particle size of less than 10 μm is used for electroplating tools, wire saws and the like, and the micro powder with high impurity content is easy to form hard lumps and is difficult to disperse, so that the quality of diamond tools and products is seriously influenced. At present, most of artificial diamonds used in industry are diamond micropowder prepared by an explosion method or a drum-type ball milling method, but the particle morphology regularity of the synthesized diamond micropowder is not good, and the proportion of the particle morphology in a sheet shape or a cuboid shape is still large. Such non-spheroidal diamond particles may cause cleavage, breakage, etc. due to the anisotropy of diamond crystals and uneven stress, which seriously affects the mechanical properties thereof, and may also cause uneven particle size distribution and uneven stress, which affects the precision polishing and grinding effect. Meanwhile, the diamond fine powder often contains impurities such as graphite, amorphous carbon, pyrophyllite, catalytic metal and the like. The high impurity content can reduce the integral hardness of the diamond and influence the service performance of the deep processing tool. Therefore, purification and morphology control of diamond becomes especially necessary. Yuanlan et al studied rapid purification electrolyzers (mining research and development, 1999(3), 23-26); pichot et al use acid washing and thermal oxidation to remove impurities from Diamond fine powder (Diamond and related Materials,2008(17), 13-22). However, these methods cannot change the morphology of the diamond micropowder, and the treatment efficiency still needs to be improved. On the other hand, in order to improve the preparation efficiency of diamond powder and improve the particle morphology, the high-speed jet mill becomes an effective method (superhard material engineering, 2012(24), 46-47; superhard material engineering, 2012(24),7-12), so that the particle morphology of the diamond micropowder is greatly improved. The method utilizes the crushing principle of direct collision and grinding among high-speed moving particles, the particle morphology of the obtained diamond micro powder can be close to a sphere-like shape without shaping, and the particle morphology of the diamond micro powder can be closer to the sphere-like shape.

Disclosure of Invention

In order to solve the problems, the method provides an efficient treatment method of the diamond micro powder, and the continuous synchronous operation of improving the appearance of the diamond micro powder particles and removing impurities is realized. The ultrasonic wave assistance is applied while the process of removing graphite, amorphous carbon, inclusions and the like on the surface of the diamond micro powder through the argon, hydrogen and oxygen mixed plasma cleaning with the assistance of the negative bias voltage, so that the diamond micro powder particles are fully dispersed due to ultra-high speed collision and fully contacted with the plasma, not only can more effectively and fully remove impurities, but also can make the surface bulges of the powder particles be etched by the plasma to be more fully and uniformly eliminated, and the particle shape is closer to a sphere-like shape. And meanwhile, uniform spheroidization of the shape of the diamond micropowder and full removal of impurities are realized. And the treated diamond micro powder is cooled in a vacuum environment, and meanwhile, the untreated diamond micro powder is put in, so that uninterrupted efficient treatment of the diamond micro powder is realized. Further improving the processing efficiency of obtaining the spherical diamond-like micro powder with uniform and pure shape.

The technical scheme of the invention is as follows:

a high-efficiency processing method of diamond micropowder, which is characterized in that diamond micropowder preheated to 600-900 ℃ is conveyed to a deposition table in a microwave plasma chemical vapor deposition chamber by a conveying device under the vacuum condition. The mixed plasma of argon, hydrogen and oxygen is used for etching treatment at the temperature of 600-900 ℃ and ultrasonic waves and negative bias voltage are applied for assistance, so that the diamond micro powder particles collide with each other and the diamond micro powder is promoted to be uniformly etched by the plasma, irregular protrusions on the surfaces of the diamond particles and impurities such as non-diamond in the micro powder are fully eliminated, and the pure diamond micro powder with a spherical shape is obtained. And then the processed diamond micro powder is taken out under the vacuum condition through a conveying and taking-out device at the other side and is synchronously cooled. Meanwhile, the next batch of diamond micropowder is conveyed and the treatment process is repeated uninterruptedly, so that the uninterrupted high-efficiency plasma treatment of pure and uniform spheroidal diamond micropowder particles is realized.

The high-efficiency treatment method of the diamond micropowder comprises the following specific steps:

step 1: setting of plasma environment

In order to realize the etching of the diamond surface and the removal of non-diamond phases, mixed gas which adopts argon, hydrogen and oxygen as gas sources is excited to form plasma. Wherein, the argon is used as inert gas and main gas source to adjust the discharge and density of plasma; hydrogen is used as a C-C bond reaction etching gas for etching the protrusions and the non-diamond phase on the surface of the diamond particles; the oxygen is used as a strong oxidant, so that organic impurities and the like remained in the non-diamond phase and the diamond powder preparation can be effectively etched and cleaned, the etching efficiency is improved, and the diamond powder is purified. And meanwhile, the vacuum pumping rate is adjusted, the gas pressure of the processing chamber is ensured, and microwaves are introduced to realize the plasma excitation of the mixed gas.

Step 2: plasma treatment and auxiliary condition setting of diamond micro powder

The powder is vibrated by ultrasonic waves and simultaneously contacts with argon, hydrogen and oxygen plasmas regulated and controlled by bias voltage to reach the high temperature of 600-900 ℃, and the surface etching of diamond particles and the etching removal of non-diamond phases are realized. The fine powder particles are often adhered to each other by factors such as high specific surface energy and impurity residues to form clusters. In order to effectively improve the appearance control and impurity removal of diamond micropowder, an ultrasonic generator is added in a deposition table to enable the micropowder to vibrate at a high speed through ultrasonic waves so as to collide with each other, and effective dispersion is realized. Meanwhile, negative bias voltage is applied on the deposition table to adjust the state of plasma, and the surface etching of the diamond surface and the removal of non-diamond phases are accelerated through the surface process activation promoted by the generated ion induced electron excitation and energy conversion and the bombardment effect of accelerated ions.

And step 3: vacuum preheating of untreated diamond micropowder

In order to realize uninterrupted plasma etching treatment, avoid destroying the vacuum environment of a plasma chemical vapor deposition system and improve the treatment efficiency and quality of diamond micropowder, the untreated diamond micropowder is subjected to preheating treatment under the vacuum condition. The influence on the air pressure of the vacuum chamber is avoided, and the cracking caused by huge internal stress brought by thermal shock caused by sudden contact of the diamond powder and the sample holder with high-temperature plasma is also avoided.

And 4, step 4: vacuum cooling of treated diamond micropowder

The plasma is also turned off to avoid affecting the vacuum environment of the process chamber, so the cooling chamber is also vacuum pumped to a pressure consistent with the process chamber before the cooling chamber vacuum valve is opened. And then taking the processed diamond micro powder out of the cooling tube cavity, and closing a vacuum valve of the cooling tube cavity to gradually cool the processed diamond micro powder.

And 5: plasma uninterrupted diamond micro powder treatment

And opening a vacuum valve of the heating pipe cavity, putting the preheated untreated diamond micro powder on a deposition table, and realizing the uninterrupted plasma etching treatment of the diamond micro powder under the condition of continuously keeping the plasma state.

Further, the gas adding, chamber pressure and plasma excitation steps in step 1 are as follows:

(1) the vacuum valve between the process chamber and the heating and cooling lumens is closed.

(2) And (3) supporting the molybdenum sample containing the diamond micro powder on a deposition table.

(3) Argon gas is slowly introduced as the main atmosphere, the vacuum suction of the chamber is opened, and the vacuum is slowly pumped until the pressure of the chamber is between 900Pa and 1.2kPa and is kept.

(4) Setting the microwave excitation power at 600W to 700W and turning on the microwave power supply to excite the plasma.

(5) And slowly introducing hydrogen with the addition amount of 10-50% of the introduction amount of the argon, and introducing oxygen with the addition amount of 1-5% of the introduction amount of the argon into the treatment chamber.

(6) Gradually increasing the microwave power to 1.5kW to 4kW, and adjusting and controlling the cavity pressure to 7kPa to 20kPa to enable the diamond micropowder temperature to reach 600 ℃ to 900 ℃.

Further, the plasma treatment and auxiliary conditions of the diamond micro powder in the step 2 are set as follows:

(1) and starting an ultrasonic generator positioned at the lower part of the deposition table to promote the vibration and mutual collision of the diamond micro powder.

(2) A negative bias voltage is applied to the deposition station, setting the bias voltage to-150V to-300V.

(3) And carrying out plasma etching cleaning treatment on the diamond for 20min to 60 min.

Further, the vacuum preheating step in step 3 is:

(1) putting the molybdenum sample holder containing the untreated diamond micro powder into a heating pipe cavity.

(2) And the lumen vacuum suction is turned on to heat the lumen pressure to be consistent with the chamber (7kPa to 20 kPa).

(2) And starting a heating assembly of the heating pipe cavity, and adjusting the heating temperature to keep the temperature consistent with the temperature of the diamond micro powder being etched in the processing chamber (600-900 ℃).

Further, the vacuum cooling step of the diamond micropowder after the treatment in the step 4 is as follows:

(1) the pressure of the cooling lumen was reduced to match the process chamber pressure by vacuum suction (7kPa to 20 kPa).

(2) And opening a vacuum valve between the cooling tube cavity and the processing chamber, taking the processed diamond micro powder and the molybdenum support out to the cooling tube cavity, and closing the vacuum valve again. And cooling the diamond micropowder to room temperature.

Further, the step 5 of uninterrupted plasma diamond micropowder treatment comprises the following steps:

keeping the plasma state, opening a vacuum valve between the heating tube cavity and the processing chamber, and putting the preheated molybdenum sample holder containing the diamond micro powder on a deposition table. The uninterrupted plasma etching treatment of the diamond micropowder is realized under the condition of not changing any treatment parameter setting.

The device is characterized in that the device structure comprises a vacuum suction device, a vacuum valve, a mixed argon gas, oxygen gas and hydrogen gas input pipe, a plasma processing chamber, a plasma generator, a sample holder, diamond micro powder, a deposition table, an ultrasonic generator, a negative bias voltage device, a heating device, a conveying and placing device, a conveying and taking device and a cooling device; the concrete connection mode is as follows:

(1) the heating tube cavity and the cooling tube cavity are respectively communicated with the plasma processing chamber, are positioned at two ends of the vacuum chamber and are positioned on the same horizontal plane with the deposition table.

(2) Vacuum valves are arranged between the heating tube cavity and the plasma processing chamber and between the cooling tube cavity and the plasma processing chamber, and heating and cooling devices are respectively arranged on the tube cavities.

(3) The conveying and taking-in device and the taking-out device are respectively arranged in the heating tube cavity and the cooling tube cavity.

(4) An ultrasonic generator and a negative bias voltage generator are arranged at the lower part of the deposition table.

(5) Vacuum suction ports are arranged in the plasma processing chamber, the heating tube cavity and the cooling tube cavity.

The key of the implementation process of the invention is as follows:

(1) the plasma gas source is a mixed gas of argon, hydrogen and oxygen. Wherein, the argon is used as inert gas and main gas source to adjust the discharge and density of plasma; hydrogen is used as reactive etching gas of C-C bonds for etching the protrusions and the non-diamond phase on the surface of the diamond particles; the oxygen is used as a strong oxidant, so that organic impurities and the like remained in the non-diamond phase and the diamond powder preparation can be effectively etched and cleaned, and the etching efficiency and the diamond powder impurity removal efficiency are further improved.

(2) The plasma treatment of the diamond micropowder can adopt a microwave plasma chemical vapor deposition system or a radio frequency plasma chemical vapor deposition system or a hot wire chemical vapor deposition system.

(3) Agglomeration is the inevitable behavior of the micropowder. The surface energy of the diamond micro powder is very high, the surface group activity is large, in order to reduce the energy of the system, particles are often close to each other to reduce the surface energy and the activity to reach a stable state with lower energy, and the process is a spontaneous process. The ultrasonic wave is adopted for assistance, linear alternating vibration action is generated by means of ultrasonic wave energy, and the energy of the action is mainly reflected in the equivalent stress action of vibration, acceleration impact and sound pressure shearing among mass points of a medium. The rapid irregular movement of the diamond micro powder can be realized through the assistance of ultrasonic vibration, so that each surface of the diamond micro powder particles can contact with plasma. Meanwhile, the impurities such as amorphous carbon and graphite in the powder can be fully contacted with the plasma by continuous particle vibration so as to be effectively removed.

(4) A negative bias voltage is applied to the deposition station by applying a bias voltage to the plasma chemical vapor deposition system having the bias voltage. The position and the state of the plasma are adjusted to be fully contacted with the diamond micro powder, the surface process activation of the plasma induced electron excitation and energy conversion promotion generated by the plasma, the shallow surface layer bombardment of accelerated ions and the subsurface atom replacement effect are utilized to accelerate the etching of the diamond surface bulge, and the decomposition and removal of impurities such as non-diamond are accelerated.

(5) In order to realize the high-efficiency treatment of the diamond micropowder, uninterrupted plasma needs to be ensured. Therefore, before putting in new diamond micropowder and taking out the processed diamond micropowder each time, the preheating pipe cavity and the cooling pipe cavity are required to be vacuumized, the pressure in the pipe cavity is ensured to be the same as the pressure in the diamond micropowder processing chamber, and therefore, the influence on the plasma is avoided, and the stability of the plasma is ensured.

(6) Before the untreated diamond micropowder is placed on a deposition table to contact with uninterrupted plasma, the diamond micropowder needs to be subjected to preheating treatment. Thereby avoiding the possible fragmentation caused by the thermal shock brought by the direct contact of the diamond micropowder and the sample holder with high-temperature plasma at room temperature.

Compared with the prior art, the invention has the beneficial effects that:

the shape regularity of the particles of the multi-purpose artificial diamond micro powder in the industry is not good, and the proportion of the particles in the shape of a sheet or a cuboid is still large. Such non-spheroidal diamond particles may cause cleavage, breakage, etc. due to the anisotropy of diamond crystals and uneven stress, which seriously affects the mechanical properties thereof, and may also cause uneven particle size distribution and uneven stress, which affects the polishing and grinding effects. Meanwhile, the diamond fine powder often contains impurities such as graphite, amorphous carbon, pyrophyllite, catalytic metal, and the like. The high impurity content can reduce the integral hardness of the diamond and influence the use performance of the deep processing tool. At present, the shape of the diamond micro powder cannot be changed by the main purification method, and the treatment efficiency still needs to be improved. On the other hand, methods for improving the morphology of particles do not eliminate the accompanying impurities in the micropowder. The method provides an efficient treatment method of the diamond micro powder, and continuous improvement of the shape of diamond micro powder particles and impurity removal are achieved at the same time. The ultrasonic wave assistance is applied while the negative bias voltage assisted argon, hydrogen and oxygen mixed plasma etching cleaning process is used for removing graphite, amorphous carbon, impurities and the like on the surface of the diamond micro powder, so that the diamond micro powder particles are fully dispersed due to ultra-high speed collision and fully contacted with the plasma, more effective and full impurity removal can be realized, the protrusions on the surface of the powder particles can be removed by plasma etching more fully and uniformly, and the particle shape is closer to a sphere-like shape. And meanwhile, uniform spheroidization of the shape of the diamond micropowder and full removal of impurities are realized. And the treated diamond micro powder is cooled in a vacuum environment, and meanwhile, the untreated diamond micro powder is put in, so that the efficient continuous treatment of the uninterrupted diamond micro powder is realized. Further improving the processing efficiency of obtaining the spherical diamond-like micro powder with uniform and pure shape.

Drawings

Fig. 1 is a structural view of an apparatus for efficiently processing diamond fine powder according to the present invention, which includes:

the device comprises a vacuum pumping device 1, a vacuum valve 2, a mixed argon, oxygen and hydrogen input pipe 3, a plasma processing chamber 4, a plasma generator 5, a sample holder 6, diamond micropowder 7, a deposition table 8, an ultrasonic generator 9, a negative bias voltage device 10, a heating device 11, a conveying and placing device 12, a conveying and taking device 13 and a cooling device 14.

Detailed Description

The technical scheme of the invention is further explained by combining the specific embodiment

Detailed description of the invention

(1) And closing a vacuum valve between the plasma processing chamber and the heating pipe cavity and the cooling pipe cavity, and supporting the molybdenum sample containing the diamond micro powder on a deposition table. Argon gas is slowly introduced as a main atmosphere, the chamber is opened for vacuum suction, and the vacuum is slowly pumped until the pressure of the chamber is 900Pa and is kept. Setting the exciting power at 600W and turning on the microwave power supply to excite the plasma. (2) And slowly introducing hydrogen with the addition of 10% of the introduction amount of the argon, and introducing oxygen with the addition of 1% of the introduction amount of the argon into the treatment chamber. Gradually increasing the microwave power to 1.5kW, adjusting and controlling the cavity pressure at 7kPa to enable the temperature of the diamond micropowder to reach 600 ℃. (3) And starting an ultrasonic generator positioned at the lower part of the deposition table to promote the vibration and mutual collision of the diamond micro powder, and applying negative bias voltage of-150V to the deposition table. And carrying out ultrasonic and negative bias voltage assisted plasma etching on the diamond micro powder for 60 min. (4) And (3) putting the molybdenum sample holder containing the untreated diamond micro powder into a heating pipe cavity, and starting the pipe cavity for vacuum suction to ensure that the pressure of the heating pipe cavity is consistent with that of the chamber (7 kPa). And starting a heating assembly of the heating pipe cavity, and adjusting the heating temperature to keep the temperature consistent with the temperature of the diamond micro powder being etched in the processing chamber (600 ℃). (5) The pressure of the cooling lumen was reduced to match the process chamber pressure (7kPa) by vacuum suction. And opening a vacuum valve between the cooling tube cavity and the processing chamber, taking the processed diamond micro powder and the molybdenum sample support out to the cooling tube cavity, and closing the vacuum valve again. And taking out the diamond micro powder after the temperature of the diamond micro powder is reduced to the room temperature. (6) And opening a vacuum valve between the heating tube cavity and the processing chamber, and placing the preheated molybdenum sample holder containing the diamond micro powder on a deposition table. The uninterrupted plasma etching treatment of the diamond micropowder is realized under the condition of not changing any treatment parameter setting. The one-time complete process of uninterrupted continuous treatment of putting in and taking out the diamond micro powder is realized.

Detailed description of the invention

(1) And closing a vacuum valve between the plasma processing chamber and the heating pipe cavity and the cooling pipe cavity, and supporting the molybdenum sample containing the diamond micro powder on a deposition table. Argon was slowly bubbled as the main atmosphere and the chamber vacuum was opened and evacuated slowly until the chamber pressure was at 1kPa and maintained. Setting the exciting power at 700W and turning on the microwave power supply to excite the plasma. (2) And slowly introducing hydrogen with the addition amount being 30% of the introduction amount of the argon, and introducing oxygen with the addition amount being 5% of the introduction amount of the argon into the treatment chamber. Gradually increasing the microwave power to 3kW, adjusting and controlling the cavity pressure at 15kPa to enable the temperature of the diamond micropowder to reach 800 ℃. (3) And starting an ultrasonic generator positioned at the lower part of the deposition table to promote the vibration and mutual collision of the diamond micro powder, and applying negative bias voltage of-200V to the deposition table. And carrying out ultrasonic and negative bias voltage assisted plasma etching on the diamond micro powder for 40 min. (4) Putting the molybdenum sample holder containing the untreated diamond micro powder into a heating pipe cavity, and starting the pipe cavity for vacuum suction to ensure that the pressure of the heating pipe cavity is consistent with that of the cavity (15 kPa). And starting a heating assembly of the heating pipe cavity, and adjusting the heating temperature to keep the temperature consistent with the temperature (800 ℃) of the diamond micro powder being etched in the processing chamber. (5) The pressure of the cooling lumen was reduced to match the process chamber pressure (15kPa) by vacuum suction. And opening a vacuum valve between the cooling tube cavity and the processing chamber, taking the processed diamond micro powder and the molybdenum sample support out to the cooling tube cavity, and closing the vacuum valve again. And taking out the diamond micro powder after the temperature of the diamond micro powder is reduced to the room temperature. (6) And opening a vacuum valve between the heating tube cavity and the processing chamber, and placing the preheated molybdenum sample holder containing the diamond micro powder on a deposition table. The uninterrupted plasma etching treatment of the diamond micropowder is realized under the condition of not changing any treatment parameter setting. The one-time complete process of uninterrupted continuous treatment of putting in and taking out the diamond micro powder is realized.

Detailed description of the invention

(1) And closing a vacuum valve between the plasma processing chamber and the heating pipe cavity and the cooling pipe cavity, and supporting the molybdenum sample containing the diamond micro powder on a deposition table. Argon was slowly bubbled as the main atmosphere and the chamber vacuum was opened and slowly evacuated until the chamber pressure was at 1.2kPa and maintained. Setting the exciting power at 700W and turning on the microwave power supply to excite the plasma. (2) And slowly introducing hydrogen with the addition amount being 50% of the introduction amount of the argon, and introducing oxygen with the addition amount being 5% of the introduction amount of the argon into the treatment chamber. Gradually increasing the microwave power to 4kW, adjusting and controlling the cavity pressure at 20kPa to enable the diamond micropowder temperature to reach 900 ℃. (3) And starting an ultrasonic generator positioned at the lower part of the deposition table to promote the vibration and mutual collision of the diamond micro powder, and applying negative bias voltage of-300V to the deposition table. And carrying out ultrasonic and negative bias voltage assisted plasma etching on the diamond micro powder for 20 min. (4) Putting the molybdenum sample holder containing the untreated diamond micro powder into a heating pipe cavity, and starting the pipe cavity for vacuum suction to ensure that the pressure of the heating pipe cavity is consistent with that of the chamber (20 kPa). And starting a heating assembly of the heating pipe cavity, and adjusting the heating temperature to keep the temperature consistent with the temperature (900 ℃) of the diamond micro powder being etched in the processing chamber. (5) The pressure of the cooling lumen was reduced to match the process chamber pressure (20kPa) by vacuum suction. And opening a vacuum valve between the cooling tube cavity and the processing chamber, taking the processed diamond micro powder and the molybdenum sample support out to the cooling tube cavity, and closing the vacuum valve again. And taking out the diamond micro powder after the temperature of the diamond micro powder is reduced to the room temperature. (6) And opening a vacuum valve between the heating tube cavity and the processing chamber, and placing the preheated molybdenum sample holder containing the diamond micro powder on a deposition table. The uninterrupted plasma etching treatment of the diamond micropowder is realized under the condition of not changing any treatment parameter setting. The one-time complete process of uninterrupted continuous treatment of putting in and taking out the diamond micro powder is realized.

Claims (8)

1. A high-efficiency processing method of diamond micropowder is characterized in that the diamond micropowder preheated at 600 ℃ to 900 ℃ is conveyed to a deposition table in a microwave plasma chemical vapor deposition chamber by a conveying device under the vacuum condition; applying ultrasonic waves and negative bias voltage for assistance while etching at 600-900 ℃ by argon, hydrogen and oxygen mixed plasma so as to enable diamond micro powder particles to collide with each other and promote the diamond micro powder to be uniformly etched by the plasma, and fully eliminating irregular protrusions on the surfaces of the diamond particles and non-diamond phase impurities in the micro powder to obtain pure diamond micro powder in a similar spherical shape; then the processed diamond micro powder is taken out under the vacuum condition through a conveying and taking-out device at the other side and is synchronously cooled; meanwhile, the next batch of diamond micropowder is conveyed and the treatment process is repeated uninterruptedly, so that the uninterrupted high-efficiency plasma treatment of pure and uniform spheroidal diamond micropowder particles is realized.

2. The method for treating the diamond micropowder with high efficiency as claimed in claim 1, wherein the specific treatment process is as follows:

step 1: setting of plasma environment

In order to realize the etching of the diamond surface and the removal of non-diamond phases, mixed gas which adopts argon, hydrogen and oxygen as gas sources is excited to form plasma; wherein, argon is used as inert gas and main gas source to adjust the discharge and density state of plasma; hydrogen is used as a C-C bond reaction etching gas for etching the protrusions and the non-diamond phase on the surface of the diamond particles; the oxygen is used as a strong oxidant, so that organic impurities except the non-diamond phase and remained in the diamond powder preparation can be effectively etched and cleaned, the etching efficiency is improved, and the diamond powder is purified; meanwhile, the vacuum pumping rate is adjusted, the gas pressure of a processing chamber is ensured, and microwaves are introduced to realize the plasma excitation of the mixed gas;

step 2: plasma treatment and auxiliary condition setting of diamond micro powder

The powder is vibrated by ultrasonic waves and simultaneously contacts with argon, hydrogen and oxygen plasmas regulated and controlled by bias voltage to reach the high temperature of 600-900 ℃, so that the surface etching of diamond particles and the etching removal of non-diamond phases are realized; the micro powder particles are often adhered to each other to form clusters due to high specific surface energy and impurity residual factors, and in order to effectively improve the appearance control and impurity removal of the diamond micro powder, an ultrasonic generator is added in a deposition table to enable the micro powder to vibrate at a high speed through ultrasonic waves to collide with each other, so that effective dispersion is realized; meanwhile, negative bias voltage is applied to the deposition table to adjust the state of plasma, and the surface etching of the diamond and the removal of non-diamond phases are accelerated through the surface process activation of ion induced electron excitation, energy conversion promotion and the bombardment effect of accelerated ions generated by the plasma;

and step 3: vacuum preheating of untreated diamond micropowder

In order to realize uninterrupted plasma etching treatment, avoid damaging the vacuum environment of a plasma chemical vapor deposition system and improve the treatment efficiency and quality of diamond micro powder, the untreated diamond micro powder is subjected to preheating treatment under the vacuum condition, so that the influence on the air pressure of a vacuum chamber is avoided, and the diamond powder and a sample holder are prevented from cracking due to huge internal stress caused by thermal shock caused by sudden contact with high-temperature plasma;

and 4, step 4: vacuum cooling of treated diamond micropowder

The plasma is closed to avoid influencing the vacuum environment of the processing chamber, so that the cooling tube cavity is also vacuumized until the air pressure is consistent with that of the processing chamber before the vacuum valve of the cooling tube cavity is opened; then taking the processed diamond micro powder out of the cooling tube cavity and closing a vacuum valve of the cooling tube cavity to gradually cool the processed diamond micro powder;

and 5: plasma uninterrupted diamond micro powder treatment

And opening a vacuum valve of the heating pipe cavity, putting the preheated untreated diamond micro powder on a deposition table, and realizing the uninterrupted plasma etching treatment of the diamond micro powder under the condition of continuously keeping the plasma state.

3. A method for processing diamond micropowder with high efficiency as claimed in claim 2, wherein the steps of adding gas, chamber gas pressure and plasma excitation in step 1 are as follows:

(1) closing a vacuum valve between the processing chamber and the heating and cooling lumens;

(2) placing a molybdenum sample holder containing diamond micro powder on a deposition table;

(3) slowly introducing argon as a main atmosphere, opening a chamber for vacuum pumping, and slowly vacuumizing until the pressure of the chamber is between 900Pa and 1.2kPa and keeping;

(4) setting microwave excitation power at 600W to 700W, starting a microwave power supply, and exciting plasma;

(5) slowly introducing hydrogen with the addition amount of 10-50% of the introduction amount of argon, and introducing oxygen with the addition amount of 1-5% of the introduction amount of argon into the treatment chamber;

(6) gradually increasing the microwave power to 1.5kW to 4kW, and adjusting and controlling the cavity pressure to 7kPa to 20kPa to enable the diamond micropowder temperature to reach 600 ℃ to 900 ℃.

4. A high-efficiency processing method of diamond micropowder as claimed in claim 2, wherein the plasma processing and auxiliary conditions of the diamond micropowder in step 2 are set as follows:

(1) starting an ultrasonic generator positioned at the lower part of the deposition table to promote the vibration and mutual collision of the diamond micro powder;

(2) applying a negative bias voltage to the deposition table, and setting the bias voltage to-150V to-300V;

(3) and carrying out plasma etching cleaning treatment on the diamond for 20min to 60 min.

5. The method for treating diamond micropowder with high efficiency as claimed in claim 2, wherein the vacuum preheating step in step 3 is:

(1) putting the molybdenum sample holder containing the untreated diamond micro powder into a heating pipe cavity;

(2) opening the tube cavity for vacuum suction, so that the pressure of the heating tube cavity is consistent with that of the cavity, and the pressure is 7kPa to 20 kPa;

(3) and starting a heating assembly of the heating pipe cavity, and adjusting the heating temperature to keep the temperature consistent with the temperature of the diamond micro powder being etched in the treatment cavity, wherein the temperature is 600-900 ℃.

6. A high-efficiency processing method of diamond micropowder as claimed in claim 2, characterized in that the vacuum cooling step of the processed diamond micropowder in step 4 is:

(1) reducing the pressure of the cooling lumen to be consistent with the pressure of the processing chamber by vacuum suction, wherein the pressure is 7kPa to 20 kPa;

(2) and opening a vacuum valve between the cooling tube cavity and the processing chamber, taking the processed diamond micro powder and the molybdenum support out to the cooling tube cavity, closing the vacuum valve again, and cooling the diamond micro powder to room temperature.

7. A method for treating diamond micropowder with high efficiency as claimed in claim 2, wherein the step 5 of uninterrupted diamond micropowder treatment by plasma comprises the following steps:

keeping the plasma state, opening a vacuum valve between the heating tube cavity and the processing chamber, and putting the preheated molybdenum sample holder containing the diamond micro powder on a deposition table; the uninterrupted plasma etching treatment of the diamond micropowder is realized under the condition of not changing any treatment parameter setting.

8. An apparatus for the method of processing diamond micropowder with high efficiency according to any one of claims 1 to 7, characterized in that the apparatus structure comprises a vacuum suction, a vacuum valve, a mixed argon, oxygen, hydrogen input tube, a plasma processing chamber, a plasma generator, a sample holder, diamond micropowder, a deposition table, an ultrasonic generator, a negative bias voltage device, a heating device, a transfer-in device, a transfer-out device, a cooling device; the concrete connection mode is as follows:

(1) the heating tube cavity and the cooling tube cavity are respectively communicated with the plasma processing chamber, are positioned at two ends of the vacuum chamber and are positioned on the same horizontal plane with the deposition table;

(2) vacuum valves are arranged between the heating tube cavity and the plasma processing chamber, and the heating and cooling devices are respectively arranged on the tube cavities;

(3) the conveying and placing device and the taking-out device are respectively arranged in the heating tube cavity and the cooling tube cavity;

(4) an ultrasonic generator and a negative bias-bias voltage device are arranged at the lower part of the deposition table;

(5) vacuum suction ports are arranged in the plasma processing chamber, the heating tube cavity and the cooling tube cavity.

Images