CN106744931A - A kind of method that plasma etching graphite prepares diamond particles - Google Patents

Abstract

The invention relates to a method for preparing diamond particles by plasma etching graphite, and the invention relates to the technical field of diamond micropowder growth. The invention aims to solve the problems of high cost, low quality, difficult dispersion, uncontrollable process and limited substrate selection in the prior preparation of artificial diamond. Methods: 1. surface treatment of graphite sheet; 2. preparing diamond on graphite by plasma etching; 3. dispersing diamond particles, that is, completing the method of preparing diamond particles by plasma etching graphite. The invention is used in a method for preparing diamond particles by plasma etching graphite.

Description

A method for preparing diamond particles by plasma etching graphite

technical field

The invention relates to the technical field of diamond micropowder growth.

Background technique

Diamond has excellent physical and chemical properties, such as the highest hardness, chemical stability, thermal conductivity and thermal stability, etc., making it widely concerned and applied in many fields. However, natural diamond reserves in nature are limited, and mining is difficult, which makes natural diamonds expensive and difficult to be used in industrial production.

At present, the artificial preparation of diamond mostly adopts high temperature and high pressure (HPHT) method, using graphite as raw material and catalyst as catalyst to prepare diamond. The diamond prepared by this method contains more impurities (such as catalyst) and structural defects, and the quality is not high, so it is difficult to meet a wide range of applications, especially in high-end fields such as semiconductors. Moreover, the high temperature and high pressure method equipment is complicated, expensive, and has a high risk factor.

Microwave-assisted chemical vapor deposition (MPCVD) method is used to excite reaction gases with microwaves, without electrode pollution, stable work, easy to control accurately, and high-quality diamonds can be prepared at relatively low pressure. The carbon sources used to prepare diamond by CVD mainly include CH ₄ , C ₂ H ₂ , CH ₃ OH, C ₂ H ₅ OH, CH ₃ COCH ₃ , CH ₃ COOH, and graphite. At present, the commonly used carbon source is mainly gaseous carbon source CH ₄ , which is mixed with hydrogen and deposited diamond on the surface of the substrate under the action of microwaves. The diamond particles produced by this method are easy to form a film and are not suitable for separation. And it needs to increase the gas path of hydrocarbon gas, which is more cumbersome in experimental operation than the method of preparing diamond with graphite as the carbon source. And when using hydrocarbon gas to synthesize diamond, it is necessary to control the proportion of hydrocarbon gas well. If the concentration of hydrocarbon gas is high, the quality of the synthesized diamond will decrease, and the content of graphite and amorphous carbon will increase; if the concentration of hydrocarbon gas is low, the rate of diamond formation will decrease, and the content of synthesized diamond will decrease. Graphite is used as a carbon source to synthesize diamond with higher purity and faster reaction speed. Only a single hydrogen gas source is required, and the operation is simple and the cost is reduced.

The temperature required for the preparation of diamond by CVD method is 200 ℃ ~ 1200 ℃, and the substrate needs to be selected according to the temperature requirements. Materials with high temperature resistance and small thermal expansion coefficient should be selected to prevent the substrate from melting or cracking during the reaction and cooling process. many restrictions.

Contents of the invention

The invention aims to solve the existing problems of high cost, low quality, difficult dispersion, uncontrollable process and limited substrate selection for preparing artificial diamond, and provides a method for preparing diamond particles by plasma etching graphite.

A method for preparing diamond particles by plasma etching graphite, specifically carried out according to the following steps:

1. Surface treatment of graphite sheet:

Stick the graphite sheet to the surface layer with scotch tape, and then use absolute ethanol, acetone and deionized water to ultrasonically clean it for 10min to 20min, respectively, to obtain the cleaned graphite sheet, and place the cleaned graphite sheet in a vacuum drying oven to dry. The drying temperature is 60°C-80°C, and the drying time is 15min-30min, and the dried graphite flakes are cooled to room temperature to obtain surface-treated graphite flakes;

2. Preparation of diamond on graphite by plasma etching method:

Place the surface-treated graphite sheet in a microwave plasma chemical vapor deposition device, and deposit it under the conditions of a hydrogen flow rate of 50sccm to 1000sccm, a temperature of 200°C to 1200°C, a pressure of 100mbar to 500mbar and a microwave power of 1800W to 5000W. 30min～24h, get the diamond prepared by plasma etching graphite;

3. Disperse diamond particles:

Scrape the diamond prepared by plasma etching graphite from the surface of the graphite sheet to obtain agglomerated diamond particles, grind and beat the agglomerated diamond particles with a stainless steel mortar for 25 minutes to 35 minutes to obtain ground diamond particles, and heat them in a water bath at a temperature of 50 Under the condition of ℃～80℃, place the ground diamond particles in sulfuric acid with a mass percentage of 20%～70% for 30min～1h, and then wash the diamond particles with deionized water until the pH of the washing liquid is 7, and then successively Ultrasonic cleaning with acetone and alcohol for 25 minutes to 35 minutes respectively to obtain cleaned diamond particles, and finally placing the cleaned diamond particles in a vacuum drying oven for drying, that is, completing the method for preparing diamond particles by plasma etching graphite.

The beneficial effect of the invention is that solid graphite is used as the carbon source and the substrate, and diamond particles can be directly grown on the graphite under the bombardment etching of the hydrogen plasma. Compared with the use of gaseous carbon sources to grow diamonds, graphite can be used as both a carbon source and a matrix, which saves the trouble of selecting substrate materials, is simple to operate, and improves the quality and quantity of prepared diamonds. The composition is almost the same as that of natural diamonds, and the size can reach Micron. And the prepared agglomerated diamond can be dispersed only after simple treatment. Compared with other processing methods for preparing diamond, the processing method of diamond prepared by etching solid graphite with hydrogen plasma is simpler, faster, more economical and environmentally friendly.

The invention is used in a method for preparing diamond particles by plasma etching graphite.

Description of drawings

Fig. 1 is the magnified 10000 times scanning electron micrograph of the diamond prepared by the plasma etching graphite prepared in embodiment 1 step 2;

Fig. 2 is the magnified 1300 times scanning electron micrograph of the diamond prepared by the plasma etching graphite prepared in embodiment 1 step 2;

Fig. 3 is the X-ray diffraction pattern of the diamond prepared by the plasma etching graphite prepared in embodiment one step two; 1 is the (111) crystal plane of diamond, 2 is the (220) crystal plane of diamond, and 3 is the (311) crystal plane of diamond ) crystal face, 4 is the (400) crystal face of diamond, and 5 is the (331) crystal face of diamond;

Fig. 4 is laser Raman spectrogram, and 1 is natural diamond, and 2 is the diamond prepared by plasma etching graphite prepared in embodiment one step two, and 3 is the polycrystalline graphite sheet described in embodiment one step one;

Fig. 5 is the scanning electron micrograph of the highly dispersed diamond particle that embodiment one prepares magnifies 1500 times;

Fig. 6 is a scanning electron microscope image enlarged 10,000 times of highly dispersed diamond particles prepared in Example 1.

detailed description

The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

Specific embodiment one: the method for preparing diamond particles by plasma etching graphite described in the present embodiment is specifically carried out according to the following steps:

1. Surface treatment of graphite sheet:

Stick the graphite sheet to the surface layer with scotch tape, and then use absolute ethanol, acetone and deionized water to ultrasonically clean it for 10min to 20min, respectively, to obtain the cleaned graphite sheet, and place the cleaned graphite sheet in a vacuum drying oven to dry. The drying temperature is 60°C-80°C, and the drying time is 15min-30min, and the dried graphite flakes are cooled to room temperature to obtain surface-treated graphite flakes;

2. Preparation of diamond on graphite by plasma etching method:

Place the surface-treated graphite sheet in a microwave plasma chemical vapor deposition device, and deposit it under the conditions of a hydrogen flow rate of 50sccm to 1000sccm, a temperature of 200°C to 1200°C, a pressure of 100mbar to 500mbar and a microwave power of 1800W to 5000W. 30min～24h, get the diamond prepared by plasma etching graphite;

3. Disperse diamond particles:

Scrape the diamond prepared by plasma etching graphite from the surface of the graphite sheet to obtain agglomerated diamond particles, grind and beat the agglomerated diamond particles with a stainless steel mortar for 25 minutes to 35 minutes to obtain ground diamond particles, and heat them in a water bath at a temperature of 50 Under the condition of ℃～80℃, place the ground diamond particles in sulfuric acid with a mass percentage of 20%～70% for 30min～1h, and then wash the diamond particles with deionized water until the pH of the washing liquid is 7, and then successively Ultrasonic cleaning with acetone and alcohol for 25 minutes to 35 minutes respectively to obtain cleaned diamond particles, and finally placing the cleaned diamond particles in a vacuum drying oven for drying, that is, completing the method for preparing diamond particles by plasma etching graphite.

In step 1 of this specific embodiment, the graphite sheet is glued to the surface with scotch tape, and it will be found that graphite marks have been left on the adhesive tape, and a new surface obtained by the graphite sheet.

In the second step of this specific embodiment, microwave excitation is used to generate glow discharge in the reaction chamber to ionize hydrogen molecules to form hydrogen plasma, which is used to etch graphite sheet to prepare diamond. Use a non-contact infrared thermometer to measure the surface temperature of the graphite sheet under the action of the plasma; parameters such as temperature and pressure in the reaction chamber are coupled and regulated by certain physical laws, avoiding heavy workload and inaccuracy caused by separate regulation difficulty. Therefore, the adjustment of parameters such as temperature and plasma density can be realized in linkage by precisely controlling the change of a single pressure value. Both the carbon source and the substrate in this specific embodiment are graphite, and diamond particles with an agglomerated structure can be obtained on the graphite surface bombarded by hydrogen plasma after the above steps. The gas required in this specific embodiment is mainly a single hydrogen, and an appropriate amount of inert gas, such as helium and argon, can also be added in order to change the quality and size of the synthesized diamond.

In order to improve the growth rate of diamond and increase the particle size of synthetic diamond, the graphite sheet can be ground with diamond micropowder or the graphite sheet can be put into a suspension containing diamond micropowder for ultrasonic dispersion treatment; then, in step 2 of this specific embodiment, Diamond was prepared on graphite by plasma etching.

Compared with other diamond dispersion patents in Step 3 of this specific embodiment, the method is simple, environmentally friendly, and low-cost.

The size of the diamond prepared by plasma etching graphite reaches the micron level, the growth rate is significantly higher than that of the diamond prepared on the Si substrate, and the purity is high, basically free of impurities such as graphite and amorphous carbon; and the generated diamond is easy to disperse without the aid of Mechanical equipment or chemical reagents can be dispersed with simple manual grinding. The experimental operation is also relatively simple, and no other hydrocarbon gas is required as a carbon source.

The beneficial effect of this specific embodiment is: using solid graphite as the carbon source and substrate, under the bombardment and etching of hydrogen plasma, diamond particles can be grown directly on the graphite. Compared with the use of gaseous carbon sources to grow diamonds, graphite can be used as both a carbon source and a matrix, which saves the trouble of selecting substrate materials, is simple to operate, and improves the quality and quantity of prepared diamonds. The composition is almost the same as that of natural diamonds, and the size can reach Micron. And the prepared agglomerated diamond can be dispersed only after simple treatment. Compared with other processing methods for preparing diamond, the processing method of diamond prepared by etching solid graphite with hydrogen plasma is simpler, faster, more economical and environmentally friendly.

Embodiment 2: This embodiment differs from Embodiment 1 in that the graphite flakes described in step 1 are highly oriented pyrolytic graphite flakes, flake graphite flakes, earthy graphite flakes or polycrystalline graphite flakes. Others are the same as in the first embodiment.

Embodiment 3: This embodiment differs from Embodiment 1 or Embodiment 2 in that: the size of the graphite sheet in step 1 is 10×10×1 mm to 30×30×10 mm. Others are the same as in the first or second embodiment.

Specific Embodiment 4: The difference between this embodiment and one of specific embodiments 1 to 3 is that in step 2, the graphite sheet after surface treatment is placed in a microwave plasma chemical vapor deposition device, and the hydrogen flow rate is 200 sccm and the temperature is 200 ° C. Under the conditions of ～1200℃, pressure 100mbar～500mbar and microwave power 1800W～5000W, deposit for 30min～24h. Others are the same as the specific embodiments 1 to 3.

Specific embodiment five: this embodiment is different from one of specific embodiments one to four in that: in step two, the graphite sheet after the surface treatment is placed in a microwave plasma chemical vapor deposition device, and the hydrogen flow rate is 50 sccm～1000 sccm, the temperature Under the conditions of 900°C, pressure of 100mbar-500mbar and microwave power of 1800W-5000W, deposit for 30min-24h. Others are the same as the specific embodiments 1 to 4.

Specific embodiment six: the difference between this embodiment and one of specific embodiments one to five is: in step two, the graphite sheet after the surface treatment is placed in a microwave plasma chemical vapor deposition device, and the hydrogen flow rate is 50sccm～1000sccm, the temperature is Under the conditions of 200°C-1200°C, a pressure of 200mbar and a microwave power of 1800W-5000W, deposit for 30min-24h. Others are the same as those in Embodiments 1 to 5.

Specific embodiment seven: the difference between this embodiment and one of the specific embodiments one to six is that in step two, the graphite sheet after the surface treatment is placed in a microwave plasma chemical vapor deposition device, and the hydrogen flow rate is 50sccm～1000sccm, the temperature is Deposit for 12 hours under the conditions of 200°C-1200°C, pressure 100mbar-500mbar and microwave power 1800W-5000W. Others are the same as those in Embodiments 1 to 6.

Embodiment 8: The difference between this embodiment and one of Embodiments 1 to 7 is that in step 2, the graphite sheet after the surface treatment is placed in a microwave plasma chemical vapor deposition device, and the hydrogen flow rate is 200 sccm and the temperature is 900 ° C. 1. Under the condition of pressure of 200mbar and microwave power of 1800W-5000W, deposit for 12h. Others are the same as those in Embodiments 1 to 7.

Specific embodiment nine: the difference between this embodiment and one of the specific embodiments one to eight is that in step two, the graphite sheet after the surface treatment is placed in a microwave plasma chemical vapor deposition device, and the hydrogen flow rate is 50sccm～1000sccm, the temperature is Under the conditions of 200°C to 900°C, pressure of 100mbar to 200mbar and microwave power of 1800W to 5000W, deposit for 30min to 12h. Others are the same as those in Embodiments 1 to 8.

Embodiment 10: This embodiment differs from Embodiment 1 to Embodiment 9 in that: in step 2, the graphite sheet after surface treatment is placed in a microwave plasma chemical vapor deposition device, at a hydrogen flow rate of 50 sccm to 1000 sccm and a temperature of Under the conditions of 900°C-1200°C, pressure of 200mbar-500mbar and microwave power of 1800W-5000W, deposit for 12h-24h. Others are the same as the specific embodiments 1 to 9.

Adopt the following examples to verify the beneficial effects of the present invention:

Embodiment one:

A method for preparing diamond particles by plasma etching graphite is carried out according to the following steps:

1. Surface treatment of graphite sheet:

Stick the graphite sheet to the surface layer with scotch tape, and then use absolute ethanol, acetone and deionized water to ultrasonically clean it for 10 minutes respectively to obtain the cleaned graphite sheet, and place the cleaned graphite sheet in a vacuum drying oven to dry at a temperature of at 80°C for 30 minutes, cool the dried graphite flakes to room temperature to obtain surface-treated graphite flakes;

Described graphite sheet is polycrystalline graphite sheet;

2. Preparation of diamond on graphite by plasma etching method:

The surface-treated graphite sheet was placed in a microwave plasma chemical vapor deposition device, and deposited for 12 hours under the conditions of a hydrogen flow rate of 200 sccm, a temperature of 900 °C, a pressure of 200 mbar, and a microwave power of 3000 W to obtain plasma-etched graphite. the diamond;

3. Disperse diamond particles:

Scrape the diamond prepared by plasma etching graphite from the surface of the graphite sheet to obtain agglomerated diamond particles, grind and beat the agglomerated diamond particles for 30 minutes with a stainless steel mortar to obtain the ground diamond particles, and heat them in a water bath with a temperature of 80 ° C. Under certain conditions, place the ground diamond particles in sulfuric acid with a mass percentage of 50% for 30 minutes, then wash the diamond particles with deionized water until the pH of the washing solution is 7, and then use acetone and alcohol to ultrasonically clean them for 30 minutes, respectively, to obtain The cleaned diamond particles are finally placed in a vacuum drying oven for drying to obtain highly dispersed diamond particles, which is to complete the method of preparing diamond particles by plasma etching graphite.

Using a scanning electron microscope to characterize the surface morphology of the diamond prepared by the plasma-etched graphite prepared in the second step of this embodiment, Fig. 1 is a 10000 times magnified scanning electron microscope of the diamond prepared by the plasma-etched graphite prepared in the second step of the first embodiment Figure; Fig. 2 is the magnification 1300 times scanning electron micrographs of the diamond prepared by the plasma etching graphite prepared in embodiment one step two; As can be seen from Fig. 1 and Fig. 2 test result, the material of generation has obvious diamond morphology , the size reaches tens of microns, significantly larger than the size (several microns) of diamond particles prepared with gaseous carbon source.

Utilize X-ray diffraction (X-Ray Diffraction, XRD) to detect the crystal composition of the diamond prepared by the plasma etching graphite prepared in step 2 of this embodiment, the crystal orientation and the crystallization integrity of the film; Fig. 3 is prepared by step 2 of embodiment 1 X-ray diffraction pattern of diamond prepared by plasma etching graphite; 1 is the (111) crystal plane of diamond, 2 is the (220) crystal plane of diamond, 3 is the (311) crystal plane of diamond, 4 is the (400) crystal plane of diamond ) crystal plane, and 5 is the (331) crystal plane of diamond; it can be seen from the test results in Figure 3 that the characteristic peaks of (111), (220), (311), (400), and (331) of diamond are almost non-diamond Phase XRD peaks.

Use Laser Raman Spectroscopy (Laser Raman Spectroscopy, Raman) to characterize the composition content and integrity of the diamond prepared by plasma etching graphite prepared in step 2 of this embodiment, without destroying the material structure; Figure 4 is the laser Raman Spectroscopy Fig. 1 is natural diamond, and 2 is the diamond prepared by plasma etching graphite prepared in embodiment one step two, and 3 is the polycrystalline graphite sheet described in embodiment one step one; Seen by Fig. 4 test result, 1332cm ^-1 is a typical diamond peak, graphite's D peak and G peak at 1323cm ^-1 and 1567cm ^-1 respectively, and the Raman peak of the generated diamond is 1331cm ^-1 , which is almost the same as the 1332cm ^-1 Raman peak of natural diamond.

From the above, it can be seen that the diamond prepared by plasma etching graphite prepared in step 2 of this embodiment is of high quality, almost the same composition as natural diamond, and the size can reach micron level.

Utilize the scanning electron microscope to characterize the surface morphology of the highly dispersed diamond particles prepared in this embodiment, Fig. 5 is a scanning electron microscopic image of the highly dispersed diamond particles prepared in the first embodiment enlarged 1500 times, and Fig. 6 is the height of the prepared diamond particles in the first embodiment The scanning electron microscope picture of dispersed diamond particles magnified 10,000 times; it can be seen from the figure that the diamond particles prepared in this embodiment are easy to disperse and have a good dispersion effect.

Claims (10)

1. a method for preparing diamond particles by plasma etching graphite is characterized in that a method for preparing diamond particles by plasma etching graphite is carried out according to the following steps: 1. Surface treatment of graphite sheet: Stick the graphite sheet to the surface layer with scotch tape, and then use absolute ethanol, acetone and deionized water to ultrasonically clean it for 10min to 20min, respectively, to obtain the cleaned graphite sheet, and place the cleaned graphite sheet in a vacuum drying oven to dry. The drying temperature is 60°C-80°C, and the drying time is 15min-30min, and the dried graphite flakes are cooled to room temperature to obtain surface-treated graphite flakes; 2. Preparation of diamond on graphite by plasma etching method: Place the surface-treated graphite sheet in a microwave plasma chemical vapor deposition device, and deposit it under the conditions of a hydrogen flow rate of 50sccm to 1000sccm, a temperature of 200°C to 1200°C, a pressure of 100mbar to 500mbar and a microwave power of 1800W to 5000W. 30min～24h, get the diamond prepared by plasma etching graphite; 3. Disperse diamond particles: Scrape the diamond prepared by plasma etching graphite from the surface of the graphite sheet to obtain agglomerated diamond particles, grind and beat the agglomerated diamond particles with a stainless steel mortar for 25 minutes to 35 minutes to obtain ground diamond particles, and heat them in a water bath at a temperature of 50 Under the condition of ℃～80℃, place the ground diamond particles in sulfuric acid with a mass percentage of 20%～70% for 30min～1h, and then wash the diamond particles with deionized water until the pH of the washing liquid is 7, and then successively Ultrasonic cleaning with acetone and alcohol for 25 minutes to 35 minutes respectively to obtain cleaned diamond particles, and finally placing the cleaned diamond particles in a vacuum drying oven for drying, that is, the method for preparing diamond particles by plasma etching graphite is completed. 2. a kind of plasma etching graphite according to claim 1 prepares the method for diamond particle, it is characterized in that the graphite flake described in step 1 is highly oriented pyrolytic graphite flake, flake graphite flake, earthy graphite flake or Polycrystalline graphite flakes. 3. A method for preparing diamond particles by plasma etching graphite according to claim 1, characterized in that the size of the graphite sheet described in step 1 is 10×10×1 mm to 30×30×10 mm. 4. a kind of plasma etching graphite according to claim 1 prepares the method for diamond particle, it is characterized in that in step 2, graphite sheet after surface treatment is placed in microwave plasma chemical vapor deposition device, at hydrogen flow rate is 200sccm , Deposition for 30 minutes to 24 hours under the conditions of a temperature of 200°C-1200°C, a pressure of 100mbar-500mbar and a microwave power of 1800W-5000W. 5. a kind of plasma etching graphite according to claim 1 prepares the method for diamond particle, it is characterized in that in step 2, graphite sheet after surface treatment is placed in microwave plasma chemical vapor deposition device, at hydrogen flow rate is 50sccm ～1000sccm, temperature 900°C, pressure 100mbar～500mbar and microwave power 1800W～5000W, deposit for 30min～24h. 6. a kind of plasma etching graphite according to claim 1 prepares the method for diamond particle, it is characterized in that in step 2, graphite sheet after surface treatment is placed in microwave plasma chemical vapor deposition device, at hydrogen flow rate is 50sccm ～1000sccm, temperature 200℃～1200℃, pressure 200mbar and microwave power 1800W～5000W, deposit for 30min～24h. 7. a kind of plasma etching graphite according to claim 1 prepares the method for diamond particle, it is characterized in that in step 2, graphite sheet after surface treatment is placed in microwave plasma chemical vapor deposition device, at hydrogen flow rate is 50sccm Deposit for 12 hours under the conditions of ～1000sccm, temperature 200℃～1200℃, pressure 100mbar～500mbar and microwave power 1800W～5000W. 8. a kind of plasma etching graphite according to claim 1 prepares the method for diamond particle, it is characterized in that in step 2, graphite sheet after surface treatment is placed in microwave plasma chemical vapor deposition device, at hydrogen flow rate is 200sccm , under the conditions of temperature 900°C, pressure 200mbar and microwave power 1800W-5000W, deposit for 12h. 9. a kind of plasma etching graphite according to claim 1 prepares the method for diamond particle, it is characterized in that in step 2, graphite sheet after surface treatment is placed in microwave plasma chemical vapor deposition device, at hydrogen flow rate is 50sccm ～1000sccm, temperature 200℃～900℃, pressure 100mbar～200mbar and microwave power 1800W～5000W, deposit for 30min～12h. 10. a kind of plasma etching graphite according to claim 1 prepares the method for diamond particle, it is characterized in that in step 2, graphite sheet after surface treatment is placed in microwave plasma chemical vapor deposition device, at hydrogen flow rate is 50sccm ～1000sccm, temperature 900℃～1200℃, pressure 200mbar～500mbar and microwave power 1800W～5000W, deposit for 12h～24h.