Growth method of progressive transition color blue diamonds

Abstract

The invention discloses a progressive transition color blue diamond growth method, which is characterized in that after a first round of growth, a boron element is added for at least one round of growth. The surface of the cut finished diamond is observed to be blue in up-down transition, the blue transition is gradual, and the light transmittance is good.

Description

Technical Field

[0001] The invention relates to the technical field of diamond processing, and in particular to a method for growing a blue diamond with a gradual transitional color. Background Art

[0002] The market for artificially grown diamonds is gradually expanding, especially in the jewelry market. Colored diamonds such as blue diamonds are rare and valuable in nature. Artificially grown blue diamonds are a means to expand production, increase sales, enhance the value of jewelry and meet people's consumption needs.

[0003] There are currently two methods for artificially growing diamonds: one is the high-temperature and high-pressure HPHT method; the other is the MPCVD microwave plasma method. High-temperature and high-pressure blue diamonds are artificially grown by adding boron to graphite or catalyst alloys, and then subjected to high pressure 5G-6G and a high temperature of about 1300 degrees for about a week. The MPCVD method is mainly cultivated by hydrogen, methane and diborane in a vacuum chamber at about 900 degrees. In addition, the CVD method can also change the color of the grown white diamonds by electron irradiation at high temperature.

[0004] Blue diamonds are loved by everyone because of their clear and beautiful color and preciousness. Blue diamonds are also suitable for daily wear because they are hard and wear-resistant, and are the hardest in nature. The fire, transparency and brightness of blue diamonds are unmatched by other sapphires, so they have unlimited prospects whether as the main stone of a wedding diamond ring or for daily wear.

[0005] At present, the boron-containing blue diamond produced by the high-temperature and high-pressure method is difficult to control, the yield rate is low, the color control deviation is large, the blue diamond has poor transparency, and the finished diamond is generally less than 1 carat, and it is impossible to stably grow finished products of more than 2 carats. Now most European and American countries produce blue diamonds through the MPCVD method. The production process does not add boron elements, but the finished white diamond is irradiated by an electron accelerator and then heated to change the color. The blue diamond produced by this method has a stable color, but the disadvantage is that the blue color is poor, and the blue color is not as transparent and glittering as high-quality natural blue diamonds. Summary of the invention

[0006] In view of the above shortcomings in the cultivation of blue diamonds, the present invention provides a method for growing blue diamonds with gradual transition colors based on the MPCVD microwave plasma method. The present invention increases the boron content by intermittently adding diborane gas during the production process to achieve a blue transition. The grown blue diamonds are easy to control the color change, and the shades and depths can be freely determined. The key is that, like natural blue diamonds, the blue color is displayed by the boron element entering the diamond body rather than by irradiation.

[0007] In order to achieve the above-mentioned object of the invention, the method for growing a gradually transitional blue diamond of the present invention is to add boron element after the first round of growth to perform at least one more round of growth.

[0008] In a preferred embodiment of the present invention, the boron element is added in the form of diborane gas.

[0009] In a preferred embodiment of the present invention, the amount of boron added in the next round of growth is greater than the amount of boron added in the previous round of growth.

[0010] In a preferred embodiment of the present invention, the amount of boron added in the next round of growth is 2 to 3 times the amount of boron added in the previous round of growth.

[0011] In a preferred embodiment of the present invention, the finished diamond after cutting is 1.5 to 5.0 carats.

[0012] Due to the above technical solution, the surface of the finished diamond after cutting in the present invention is observed to be blue with a gradual transition from top to bottom and good light transmittance. The present invention focuses on adding diborane from the second round to allow boron atoms to replace carbon atoms to show blue. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is one of the schematic diagrams of a finished diamond according to Example 1 of the present invention.

[0014] Figure 2 One of the schematic diagrams of the finished diamond of Example 1 of the present invention DETAILED DESCRIPTION

[0015] The present invention is described in detail below in conjunction with embodiments.

[0016] Example 1

[0017] The method for growing a blue diamond with a gradual transitional color in this embodiment comprises the following steps:

[0018] Step 1: Take a 12X12 mm diamond seed (of course not limited to 12X12 mm diamond seed, any size of seed can be used), select a defect-free surface, and polish it with diamond powder W14 for 30 minutes to reduce the surface roughness and defects of the seed;

[0019] Step 2: Mechanical polishing is followed by chemical cleaning. Chemical cleaning is performed by boiling with aqua regia (hydrochloric acid plus nitric acid) for 30 minutes, ultrasonic cleaning with deionized water for 10 minutes, ultrasonic cleaning with acetone for 30 minutes, and finally washing with anhydrous alcohol and deionized water alternately for 30 minutes, and then drying in an oven for later use;

[0020] Step 3: Plasma etching treatment is to place the cleaned and dried seed crystal in the MPCVD furnace chamber, with the growth surface of the seed crystal facing up; after evacuating to 0.1 Torr, 400 Sccm of hydrogen is introduced for hydrogen plasma etching and hydrogen-oxygen mixed plasma etching treatment, and the pressure of the reaction chamber is controlled between 100 and 200 Torr, the microwave power is 3500 to 5500W, the hydrogen flow rate is 400 Sccm, and the oxygen flow rate is 5 Sccm. Etching for 60 minutes, then the oxygen is removed, and hydrogen is used for etching for 20 minutes to maintain the temperature of 800 to 950 degrees for growth;

[0021] Step 4: For the growth of blue diamonds, increase hydrogen to 400 Sccm to 500 Sccm, slowly increase the gas pressure and power at 100 Torr and 200 Torr, power 5000W to 10000W, temperature stabilized at 800 to 950 degrees, release methane 30 to 50 Sccm, and continue growing for 80 to 120 hours, then stop the first round of growth;

[0022] Step 5: After the first round of growth of 80 to 120 hours, the blue diamond needs to be laser-removed for 4 weeks due to the appearance of polycrystalline on the edge. The surface is cut flat, and then the growth surface is re-polished with W14 diamond powder. The second round of growth is carried out after repeating the 1.2.3. process;

[0023] Step 6: Repeat the blue diamond growth process in step 4 for the second round of growth, add 0.05 Sccm of diborane and grow continuously for 80 to 120 hours, then take out and repeat steps 1, 2, and 3 to carry out the third round of growth.

[0024] Step 7: In the third round of growth, in order to gradually transition to blue, the diborane level needs to be increased from 0.05 Sccm to 0.10 Sccmm. The growth time is about 80 to 120 hours. After the growth, take it out and repeat steps 1, 2 and 3 to carry out the fourth round of growth.

[0025] Step 8: Repeatedly add 0.30Sccmm of diborane for the fourth round of growth. After four rounds of growth, the blue diamond is 1.5 to 5.0 carats (finished diamond after cutting, see Figure 1 and Figure 2 ) The surface is observed to be blue with a gradual transition from top to bottom and good light transmittance.

[0026] The amount of diborane added in each of the above steps is the amount of diluted diborane gas, and the actual amount may be greater or less than the process addition amount, which is determined by the gradual blue color of the blue diamond. Of course, it is not limited to diborane, and can also be other substances containing boron.

[0027] The above-mentioned 2nd to 4th rounds of growth can be reduced or increased.

[0028] Example 2

[0029] The blue diamond growth method of this embodiment includes the following steps:

[0030] Step 1: Take a 12X12mm diamond seed (not limited to 12X12mm diamond seed, any size of seed will do), select a defect-free surface and polish it with diamond powder W14 for 30 minutes to reduce the surface roughness and defects of the seed.

[0031] Step 2: After mechanical polishing, chemical cleaning is performed. The chemical cleaning is performed by boiling in aqua regia (hydrochloric acid plus nitric acid) for 30 minutes, ultrasonic cleaning with deionized water for 10 minutes, and then ultrasonic cleaning with acetone for 30 minutes. Finally, wash alternately with anhydrous alcohol and deionized water for 30 minutes, and put into the oven for drying.

[0032] Step 3: Plasma candle treatment is to put the cleaned and dried seed crystal in the MPCVD furnace chamber with the growth side facing up. After evacuating to 0.1 Torr, input 500 Sccm of hydrogen for hydrogen plasma candle treatment and hydrogen-oxygen mixed plasma candle treatment. Control the reaction chamber pressure between 100 and 200 Torr, microwave power 4000 to 6000 W, hydrogen flow rate 500 Sccm, oxygen 5 Sccm candle treatment for 60 minutes, then remove oxygen and use hydrogen candle treatment for 20 minutes, maintaining the temperature at 900 to 1000 degrees for growth.

[0033] Step 4: For the growth of blue diamonds, increase the hydrogen flow rate to 500 Sccm, slowly increase the gas pressure and power at 150 Torr, power 5000W~8000W, temperature stabilized at 900-1000 degrees, release methane 50 Sccm, grow continuously for 100 hours, and stop the first round of growth.

[0034] Step 5: After the first round of growth of the blue diamond for about 100 hours, due to the appearance of polycrystals on the edge, 4 weeks of polycrystals need to be removed by laser, the surface is cut flat, and then the growth surface is re-polished with W14 diamond powder. After repeating processes 1, 2, and 3, the second round of growth is carried out. The second round of growth repeats the blue diamond growth process in step 4, adding diborane 0.15Sccw for continuous growth for 100 hours, taking it out and repeating steps 1, step 2, step 3 before the third round of growth.

[0035] Step 6: In the third round of growth, in order to gradually transition to blue, the diborane needs to be increased from 0.15 Sccm to 0.30 Sccm and the growth time is 100 hours. After the growth, take it out and repeat steps 1, 2, and 3 to carry out the fourth round of growth.

[0036] Step 7: The 4th round of growth is performed by repeatedly adding 0.50 Sccm of diborane. After the 4th round of growth, the blue stone in the 1.5-5.0 carat (finished diamond after cutting) surface is observed as a dark blue diamond with average blue light transmittance.

[0037] Comparison conclusion between Example 2 and Example 1

[0038] Compared with Example 1, Example 2 changes the flow rate of diborane from 0.05 Sccm in the second round to 0.15 Sccm, from 0.10 Sccm in the third round to 0.30 Sccm, and from 0.30 Sccm in the fourth round to 0.50 Sccm. Since diborane has a strong blue color rendering ability and other growth processes remain basically unchanged, in Example 2, the blue diamond gradient process is not obvious. Compared with Example 1, the blue color is too deep, the light transmittance is weak, and there is no flashing light.

[0039] Example 3

[0040] The method for growing a blue diamond with a gradual transitional color in this embodiment comprises the following steps:

[0041] Step 1: Take a 12X12 mm diamond seed and select the defect-free surface. Use diamond powder W14 to polish for 30 minutes to reduce the surface roughness and defects of the seed.

[0042] Step 2: Mechanical polishing and chemical cleaning. For chemical cleaning, use aqua regia (hydrochloric acid plus sodium chloride) to boil for 30 minutes, use deionized water for ultrasonic cleaning for 10 minutes, then use acetone for ultrasonic cleaning for 30 minutes, and finally use anhydrous alcohol and deionized water to wash alternately for 30 minutes, and put it into the oven to dry for later use.

[0043] Step 3: Plasma candle treatment is to place the cleaned and dried seed crystal in the MPCVD furnace chamber with the growth side of the seed crystal facing up. After evacuating to 0.1 torr, introduce 500 Sccm of hydrogen for hydrogen plasma candle treatment and hydrogen-oxygen mixed plasma candle treatment. The reaction chamber pressure is controlled between 100 and 200 torr, the microwave power is 3500 to 5000W, the hydrogen flow rate is 500 Sccm, and the oxygen is 5 Sccm. The candle is burned for 60 minutes, and then the oxygen is removed and the hydrogen is used for 20 minutes to maintain the temperature of 800 to 950 degrees for growth.

[0044] Step 4: Growth of blue diamonds. Slowly increase the gas pressure and power. When the pressure is 100 Torr and 200 Torr, the power is 5000W-10000W, the temperature is stabilized at 800-950 degrees, and methane is released at 30-50 Sccm. Grow continuously for 80-120 hours and stop the first round of growth.

[0045] Step 5: After the first round of growth of blue diamonds for 80 to 120 hours, due to the appearance of edge polycrystals, 4 weeks of polycrystals need to be laser removed, the surface is cut flat, and then the growth surface is re-polished with W14 diamond powder. After repeating processes 1, 2, and 3, the second round of growth is carried out. The second round of growth repeats the blue diamond growth process in step 4, adding diborane 0.10Sccw for continuous growth for 80 to 120 hours, taking out and repeating steps 1, step 2, and step 3 before the third round of growth. After about 120 hours of growth, the edge polycrystals must be cut and re-polished, otherwise surface defects are likely to occur, affecting the growth of the diamond surface.

[0046] Step 6: For the third round of growth, repeat the blue diamond growth process in step 4, add 0.10 Sccm of diborane and grow continuously for 120 hours. After the growth is completed, repeat steps 1, 2 and 3 for the fourth round of growth.

[0047] Step 7: Repeat the fourth round of growth by implementing process steps 1, 2, 3, and 4 of Case 1 until the growth is completed.

[0048] Comparison conclusion between Example 2 and Example 1

[0049] In Example 3, compared with Example 1, the flow rate of diborane was changed from 0.05 Sccm in the second round to 0.10 Sccm, and the growth with a flow rate of 0.10 Sccm of diborane was repeated in the third round. The fourth round of growth was not added with borane and was white like the first round. The diamonds after growth had good light transmittance, but the blue color was monotonous and not very dynamic.

Claims

1. The method of growing a blue diamond with a gradual transition color is characterized by After the first round of growth, boron is added for at least one more round of growth.

2. The method for growing a blue diamond with a gradual transitional color according to claim 1, characterized in that: The boron element is added in the form of diborane gas.

3. The method for growing a blue diamond with a gradual transitional color according to claim 1 or 2, characterized in that: The amount of boron added in the next round of growth is greater than the amount of boron added in the previous round of growth.

4. The method for growing a blue diamond with a gradual transitional color according to claim 3, characterized in that: The amount of boron added in the next round of growth is 2 to 3 times the amount of boron added in the previous round of growth.

5. The method for growing a blue diamond with a gradual transitional color according to claim 1, characterized in that: The finished diamond after cutting is 1.5 to 5.0 carats.

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