How are artificial diamonds made?

Publication number RU2131763C1 RU2131763C1 RU97114492A RU97114492A RU2131763C1 RU 2131763 C1 RU2131763 C1 RU 2131763C1 RU 97114492 A RU97114492 A RU 97114492 97114492A RU 97114492 A RU97114492 A RU 2131763A RU 1 C2131763 RU1 C2131763 RU 1C1997 Authority RU Russia Prior art keywords fullerene graphite diamond pressure diamonds Prior art date 08 -22-97114492 Application number RU97114492A Other languages ​​English ( en ) Other versions RU1997A ( ru Inventor A.Ya. Vul S.V. Kidalov S.V. Kozyrev V.M. Davidenko V.A. Yashin S.S. Ordanyan V .S. Lysanov Original Assignee Closed Joint Stock Company “Scientific and Technical Agency “Intellect” Open Joint Stock Company “Abrasive Plant “Ilyich” Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.) 08-22-1997 Filing date 08-22-1999 Publication date 06-20-1997 08-22-1997 Application filed by Closed Joint Stock Company “Scientific and Technical Agency” Intellect”, Open Joint Stock Company “Ilyich Abrasive Plant” filed Critical Closed Joint Stock Company “Scientific and Technical Agency “Intellect” 08-22-97114492 Priority to RU2131763A priority Critical patent/RU1C1998/ru 08-20-1998 Priority to PCT/ RU000273/1999010274 priority patent/WO1A1999/ru 06-20-1999 Application granted granted Critical 06-20-97114492 Publication of RU97114492A publication Critical patent/RU1999A/ru 06-20-2131763 Publication of RU1C2131763 publication Critical patent/RU1 XNUMXCXNUMX/en

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• • B – PERFORMING OPERATIONS; TRANSPORTING
  • B01 – PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J – CHEMICAL OR PHYSICAL PROCESSES, eg CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J3/00 – Processes of utilizing sub-atmospheric or super-atmospheric pressure to effect chemical or physical change of matter; Apparatus therefor
  • B01J3/06 – Processes using ultra-high pressure, eg for the formation of diamonds; Apparatus therefor, eg molds or dies
  • B01J3/062 — Processes using ultra-high pressure, eg for the formation of diamonds; Apparatus therefor, eg molds or dies characterized by the composition of the materials to be processed
  • C – CHEMISTRY; METALLURGY
  • C01 – INORGANIC CHEMISTRY
  • C01B – NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00 – Carbon; Compounds thereof
  • C01B32/25 – Diamond
  • C01B32/26 – Preparation
  • B – PERFORMING OPERATIONS; TRANSPORTING
  • B01 – PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J – CHEMICAL OR PHYSICAL PROCESSES, eg CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2203/00 — Processes utilising sub- or super atmospheric pressure
  • B01J2203/06 – High pressure synthesis
  • B01J2203/0605 – Composition of the material to be processed
  • B01J2203/061 – Graphite
  • B – PERFORMING OPERATIONS; TRANSPORTING
  • B01 – PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J – CHEMICAL OR PHYSICAL PROCESSES, eg CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2203/00 — Processes utilising sub- or super atmospheric pressure
  • B01J2203/06 – High pressure synthesis
  • B01J2203/0605 – Composition of the material to be processed
  • B01J2203/0615 – Fullerene
  • B – PERFORMING OPERATIONS; TRANSPORTING
  • B01 – PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J – CHEMICAL OR PHYSICAL PROCESSES, eg CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2203/00 — Processes utilising sub- or super atmospheric pressure
  • B01J2203/06 – High pressure synthesis
  • B01J2203/065 — Composition of the material produced
  • B01J2203/0655 – Diamond

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  Abstract

  Usage: the method for producing artificial diamonds relates to the technique of producing high-hard materials, namely the synthesis of diamonds, which are used, in particular, for the manufacture of diamond tools. The method involves exposing graphite with fullerene and a catalyst to pressure and heating in the stability range of diamonds, followed by exposure at pressure and synthesis temperature. What is new is the introduction of fullerene in an amount of 10 -2 – 6•10 -1 wt. % of the mass of graphite and the distribution of fullerene in the mass of graphite. Fullerene can be introduced in the form of fullerene-containing soot or fullerene extract. The method makes it possible to increase the yield of diamonds at pressures not exceeding 5,5 GPa. 2 salary forms, 1 illustration, 1 table.

  Description

  The invention relates to a technique for producing high-hard materials, namely to the synthesis of diamonds, used, in particular, for the manufacture of diamond tools.

  There is a known method for producing artificial diamond, which includes pulsed impact on a sample of graphite and metal with pressure and heating by passing an electric current pulse through a sample containing a metal from the group: copper, aluminum, nickel, iron with the inclusion of fine graphite particles, the average size of which is 5-10 microns , with the following ratio of components, vol.%: graphite – 5-55, metal of the specified group – 45-95 [1].

  The known method makes it possible to simplify the technology for producing diamonds, however, the known method is characterized by a low yield of diamonds.

  There is a known method for producing diamonds, which involves exposing a carbon-containing material to high pressure when heated in the stability region of the diamond. Alpha-carbine in amorphous form is used as a carbon-containing material. Alpha carbyne may contain carbon in an amount of 99,0-99,9 wt. %, and heating is carried out to a temperature of 1400-1700 o C [2].

  The known method allows you to speed up the process and slightly increase the yield of diamonds, but the percentage of yield is still not high enough.

  There is a known method for producing polycrystalline diamond, which involves heating a carbon-containing material separated from the catalyst by a separating layer under pressure, followed by holding it at synthesis temperature and pressure. The material is heated at a rate of 1500-2000 degrees/s with a change in pressure at a rate of 3-4 GPa, the exposure is carried out for 0,5-5,0 s, while a material with a hardness of 0,45-5,0 GN is used as a separating layer /m 2 and dispersion of 1-10 microns. The synthesis is maintained at 1800-2100 K and a pressure of 7-8 GPa [3].

  The known method requires the use of excessively high temperatures and pressures and does not provide diamonds in the form of single crystals.

  There is a known method for producing diamond, which involves compressing a carbon-containing material to a sufficient size and heating it, followed by holding it at synthesis temperature and pressure. Fullerene of various molecular weights (from C₃₂ to C₈₄). A pressure gradient higher than 1 GPa/mm can be created in the depth of the sample. The magnitude of the main pressure can reach 15-25 GPa. Sample compression can be carried out under both hydrostatic and non-hydrostatic conditions. The pressure can be reduced by heating to a temperature below 1000 o C [4].

  The known method makes it possible to obtain high-quality diamonds, in particular polycrystalline ones, but its implementation requires the use of excessively high pressures or the creation of a pressure gradient, which complicates the equipment used.

  There is a known method for producing diamonds from an initial powdered material containing carbon as the main component, which includes exposing said material to a pressure in the range of 2-50 GPa when applying a pressure gradient to the material and simultaneous heating by irradiation of a part of the material to which the maximum pressure is applied with laser radiation. Fullerene C was taken as the main component of the powdered material₆₀ or carbon microtubes [5].

  The known method makes it possible to maintain a constant temperature of the sample for quite a long time, however, the equipment used becomes significantly more complicated.

  The closest to the claimed method for producing artificial diamonds is the method for producing diamonds, adopted as a prototype, since it coincides with the claimed method in the largest number of characteristics. The prototype method involves exposing fullerene powder, placed between two layers of graphite with a total mass of about 10% of the fullerene mass, to a pressure of 6,7 GPa and heating to a temperature of 1200-1850 o C with catalysts: nickel, cobalt and cobalt alloy [6] .

  The known prototype method makes it possible to increase the yield of diamonds to a value of about 90%, but in this case it is necessary to apply a fairly high pressure (6.7 GPa), which leads to the complication of the equipment used.

  The objective of the present invention was to develop a method for producing artificial diamonds that would provide a high yield of diamond at low pressures not exceeding 5,5 GPa.

  The problem is solved by the fact that in the method of producing artificial diamonds, which includes exposing fullerene to graphite and a catalyst and heating in the stability range of diamond, followed by exposure at the synthesis temperature, fullerene is introduced in an amount lying in the range of 10 -2 – 6•10 – 1 wt. % of the mass of graphite, and distribute it in the mass of graphite. Fullerene can be introduced in the form of fullerene-containing soot or in the form of a fullerene extract.

  It was unexpectedly discovered that if fullerene is introduced into the charge not as the main component, but in an amount of 10 -2 – 6•10 -1 wt.% of the mass of graphite and at the same time distributing it in the mass of graphite, then it turns out to be possible at relatively low pressures ( 4,5-5,5 GPa) to obtain a significantly higher yield of diamonds than in the case when the charge contains fullerene as the main carbon component.

  The resulting effect can be clearly seen from the graph shown in the drawing, which shows some results from the experimental determination of the dependence of the proportion of transition of graphite and fullerene into diamond, in wt.%, on the fullerene content in graphite, in wt.% for pressures of 4,5 GPa ( curve 1) and 5,5 GPa (curve 2).

  When the fullerene content in graphite exceeds 6•10 -1 wt.%, the yield of diamonds becomes comparable to the yield of diamonds from a graphite charge.

  When the fullerene content is below 10 -2 wt.% by weight of graphite, an increase in the diamond yield is also not observed.

  The experiments carried out by the authors showed that a necessary condition for obtaining an increased diamond yield is the distribution of fullerene in the graphite mass.

  The discovered effect is apparently due to the fact that in the above quantitative range, fullerene molecules behave as a catalyst in the formation of diamond, like some metals, due to the formation, for example, of carbides during the destructuring of fullerenes at temperatures above 800 o C.

  The inventive method for producing artificial diamonds is carried out as follows. A charge of graphite is prepared with the addition of fullerene in an amount of 10 -2 – 6•10 -1 wt.% by weight of graphite and a catalyst, for example an alloy of chromium and nickel, an alloy of chromium with manganese or an alloy of nickel, manganese and copper, by mixing in a mixer. The resulting mixture is briquetted under pressure and placed in the cavity of a thermal and electrical insulating container, covered on both sides with lids made by pressing a mixture of graphite and limestone. The container thus equipped is placed in a high-pressure apparatus and compressed to a pressure corresponding to the region of stable diamond formation, and then heated by passing an electric current through the charge to a temperature corresponding to this pressure, then maintained at this temperature and pressure for a given time. After holding, the electric current is turned off, the pressure is relieved, and the diamond synthesis product is removed. Then chemical enrichment is carried out, the resulting diamond is scattered according to grain size, and for each grain size the mechanical strength is determined, the values ​​of which determine the grade of diamond.

  Below are examples of specific implementations of the method for producing artificial diamonds.

  Prepare a charge from graphite with the addition of fullerenes C₆₀ + C₇₀ in an amount of 0,15 wt.% by weight of graphite, introducing them from a fullerene extract, and a catalyst from a nickel alloy with manganese. Mixing of the components is carried out in a mixer, achieving distribution of fullerenes in the volume of graphite. Then the charge is briquetted, subjecting it to a pressure of 10 MPa, and placed in a cylindrical container of a thermal and electrical insulating container, closed on both sides with pressed lids made of a mixture of graphite and limestone. The equipped container is placed in a high-pressure apparatus of the “anvil with a hole” type, compressed to a pressure of 4,5 GPa, heated by passing an electric current through the charge to a temperature of 1250 o C and maintained at these parameters for 10 minutes. After holding, the heating is turned off, the pressure is removed and the synthesis product is removed. After chemical enrichment, the proportion of transition of graphite into diamond is determined, which averaged 33,7% from one sintering.

  The same operations are performed at the same pressures, holding times and temperatures as in example 1, but the mixture is prepared without adding fullerene. The percentage of transition from graphite to diamond averaged 22,6% per sintering.

  Perform the same operations and at the same pressures, holding times and temperatures as in example 1, but add fullerenes C₆₀ + C₇₀ in an amount of 0,01 wt. % by weight of graphite, introducing them from fullerene extract. The percentage of transition from graphite to diamond averaged 30,3% per sintering.

  Perform the same operations and at the same pressures, holding times and temperatures as in example 1, with the addition of fullerenes C₆₀ + C₇₀ in an amount of 0,12 wt.% by weight of graphite, introducing them from fullerene soot (containing 8% fullerenes). The share of transition from graphite to diamond averaged 35,0% per sintering.

  Perform the same operations and at the same pressures, holding times and temperatures as in example 1, with the addition of fullerenes C₆₀ + C₇₀ in an amount of 0,02 wt.% by weight of graphite, introducing them from fullerene soot (containing 2% fullerenes). The share of transition from graphite to diamond averaged 27,2% per sintering.

  Perform the same operations and at the same pressures, holding times and temperatures as in example 1, with the addition of fullerenes C₆₀ + C₇₀ in an amount of 0,6 wt.% by weight of graphite, introducing them from the fullerene extract. The share of transition of graphite into diamond averaged 22,7% per sintering.

  Perform the same operations and at the same pressures, holding times and temperatures as in example 1, with the addition of fullerenes C₆₀ + C₇₀ in an amount of 0,62 wt.% by weight of graphite, introducing them from the fullerene extract. The share of transition of graphite into diamond averaged 22,5% per sintering.

  The same operations are performed as in example 1, but heating is carried out to a temperature of 1350 o C at a pressure of 5,5 GPa for 90 s, with the addition of fullerenes C₆₀ + C₇₀ in an amount of 0,15 wt.% by weight of graphite, introducing them from the fullerene extract. The share of transition of graphite into diamond averaged 75,0% per sintering.

  Perform the same operations and at the same pressures, holding times and temperatures as in example 8, with the addition of fullerenes C₆₀ + C₇₀ in an amount of 0,6 wt.% by weight of graphite, introducing them from the fullerene extract. The share of transition of graphite into diamond averaged 55,0% per sintering.

  Perform the same operations and at the same pressures, holding times and temperatures as in example 8, with the addition of fullerenes C₆₀ + C₇₀ in an amount of 0,01 wt. % by weight of graphite, introducing them from fullerene extract. The percentage of transition from graphite to diamond averaged 57% per sintering.

  The same operations are performed at the same pressures, holding times and temperatures as in example 8, but without adding fullerenes. The share of transition from graphite to diamond averaged 45,0% per sintering.

  Perform the same operations and at the same pressures, holding times and temperatures as in example 8, with the addition of fullerenes C₆₀ + C₇₀ in an amount of 0,63 wt.% by weight of graphite, introducing them from the fullerene extract. The share of transition of graphite into diamond averaged 42,0% per sintering.

  The claimed method for producing artificial diamonds was tested in industrial production conditions. The use of the proposed method allows one to obtain a significant economic effect.

  Some batches of artificial diamonds obtained in the above examples were dispersed by size and then the mechanical strength of the diamond crystals was measured. The results of these measurements are shown in the table.

  References
  1. RF Patent N 1820890, IPC C 01 B 31/06, publ. 07.06. 1993
  2. Copyright certificate of the USSR N 1533221, IPC C 01 B 31/06, publ. 23.02.1993/XNUMX/XNUMX
  3. Copyright certificate of the USSR N 1340030, IPC C 01 B 31/06, publ. 15.06. 1996
  4. International application WO 93/02012, IPC C 01 B 31/00, publ. 04.02. 1993
  5. US Patent N 5360477, IPC C 30 B 29/00, publ. 01.11.1994

  6. Bocquillon G., Bogicevie C., Fabre C., Rassat A. – C₆₀ Fullerene as Carbon Source for Diamond Synthesis. – Journ. Phys. Chem. – 1993, v. 97, p. 12924-12927.

  Claims (3)

  1. A method for producing artificial diamonds, including exposing graphite with fullerene and a catalyst to pressure and heating in the stability range of the diamond, followed by holding at pressure and synthesis temperature, characterized in that fullerene is introduced in an amount of 10 -2 – 6 • 10 -1 wt. % by weight of graphite, while fullerene is distributed in the mass of graphite.

  What is the future of the synthetic diamond market, how do their production technologies differ, and is it possible to make money on these stones?

  From time immemorial, people have sought to find an alternative to expensive but attractive stones – natural diamonds. And it’s not just about their use in the jewelry business. Diamond has rare qualities – hardness and thermal conductivity, which allows it to be used for mechanical processing of hard materials and precious stones, as well as in the production of industrial drills and cutting tools.

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  The first experience in the synthesis of artificial diamond belongs to the French scientist Henri Moissan, who in 1893 obtained the first diamonds by crystallization from a solution in an iron melt. Unfortunately, the size of the resulting crystals was negligibly small. In honor of Moissan, an analogue of natural diamond, moissanite, was named, which, along with cubic zirconia, served as a cheaper substitute for natural stones until humanity learned to make artificial diamonds.

  Synthetic diamonds for industry appeared only in the middle of the 1963th century. As it became known later, the first stones suitable for technical purposes were produced by the Swedish electrical engineering company Asea in XNUMX. At the same time, the very fact of obtaining and producing diamonds was kept secret. The secret was made public only several decades later in a dispute for primacy with another US company.

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  Now the areas of application of diamond are cutting and processing tools in the form of diamond discs, tool inserts with diamond tips, diamond cups for grinding and polishing. Diamonds are used in microelectronics, power and microwave electronics, photonics, laser technology, and ionizing radiation detectors.

  

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  At the same time, there are two main technologies for the synthesis of artificial diamonds: High-Pressure High-Temperature (HPHT) technology, when stones are created at very high temperatures and pressure, and Chemical Vapor Deposition (CVD) technology, in which layer-by-layer molecular synthesis of diamond occurs from a mixture of gases methane and hydrogen under vacuum and microwave conditions. The latest technology is best suited for producing pure bulk diamonds and diamond wafers with clearly defined parameters. By controlling the synthesis recipe, this method can produce optical diamond plates with a given level of light transmission, heat-removing plates for electronics and lasers with the required thermal conductivity, and jewelry raw materials in the form of cubes with a specific color.

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  One of the new areas of application of artificial diamonds is the space industry. Thus, the startup CVD-Spark (part of the Technospark group of companies) recently produced optical diamond plates for the windows of a space device as part of the Moscow Aviation Institute’s “Sun-Terahertz” project, which was launched to the International Space Station (ISS) to study solar radiation . In general, the advantage of CVD diamond manufacturing technology over HPHT is that the former can be used to produce large-area diamond plates.

  

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  In addition, CVD-Spark diamonds are used in cases where there is a need to remove a large amount of heat from a small fuel element (microcircuit, microwave or power transistor, semiconductor or disk laser). In such cases, it is not copper (the most common material for heat sinks) that is used, but diamond, because its thermal conductivity is six times greater than that of copper.

  Diamond coating also finds its application in consumer electronics, computers, phones – now in some flagship smartphone models, diamond coating is applied to the back cover or to the processor itself so that heat is most effectively removed from the processor and dissipated on the cover.

  In medicine, diamond scalpels with diamond coating are used – during operations using them, fewer scars are formed after tissue healing.

  Artificial diamonds made using CVD technology are also used as a detector of ionizing radiation in radiation therapy machines, the so-called proton knives. When it is possible, through the use of elementary particles, protons, to focus radiation at a certain depth of human organs and carry out operations or research with very high resolution. When irradiated with protons, it is possible to influence cancer cells with high precision without damaging the cells of healthy tissues, which is why radiation therapy has now begun to spread widely in the treatment of cancer.

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  However, in such devices it is necessary to very accurately record the radiation doses that patients receive. Nowadays, the silicon radiation detectors used in these devices, which have a short service life, are being replaced by diamond detectors. In them, the diamond plate plays the role of a solid-state ionization chamber; under the influence of radiation, a very small electric current appears in the plate (electroluminescence), which is converted by the device into the amount of radiation.

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  The electroluminescence and detector properties of diamond are also used to determine the level of radiation activity in spent nuclear fuel pools at nuclear power plants, in particle accelerators to determine the position in space and the number of streams of high-energy particles.

  Diamonds out of thin air

  The technology for producing diamonds from a mixture of CVD (Chemical Vapor Deposition) gases has been developing relatively recently – since the 1980s. Its rapid growth began in the late 2000s and early 2010s, as the market began to receive requests for some artificial materials that had previously been replaced by natural ones. The fact is that artificial diamonds are about 10 times cheaper than natural ones, and can be synthesized in large sizes and with specified properties.

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  In addition, artificial diamonds have a number of advantages over natural ones. Thus, in the jewelry industry, for the manufacture of necklaces and bracelets, it is often necessary to select a number of stones of approximately the same size and color. Making jewelry from natural stones, each of which is individual, is very difficult. But it is quite possible to synthesize a number of identical diamonds artificially in just 2-3 weeks.

  

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  In industry, the advantages of artificial diamonds are even more significant: the fact is that natural stones have unwanted inclusions of other minerals. But stones obtained using CVD technology are distinguished by amazing purity. In addition, natural stones have a limited size, a few millimeters. If you need a crystal measuring 10 by 10 mm or a plate with a diameter of 25-50 mm, then such natural stones simply do not exist, but synthetic ones do. Even if some record-breaking natural stone is found, no one will cut it into plates to use in lasers, optics, electronics or detectors. Here only synthetic diamond will come to the rescue.

  In addition, established practice makes it possible to determine in advance what thermal conductivity and optical transmittance and detector sensitivity this artificial diamond plate will have. Also, at the stage of growth of synthetic diamonds, it is possible to dope them – introducing atoms of other chemical elements into the crystal lattice, obtaining from diamonds a material with semiconductor and quantum properties.

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  Typically, for technical applications, large diamond plates are first synthesized – up to 2-3 mm thick and up to 100 mm in diameter. These large plates are then laser cut into many small pieces of varying shapes and sizes to suit specific applications. Then these plates are ground and polished to achieve the required level of roughness.