RU2223220C2 - Method of preparing diamond particles, method of preparing diamond crystals, and method of preparing blanks containing diamond particles - Google Patents

Abstract

FIELD: carbon materials. SUBSTANCE: invention relates to synthesis of superhard materials, in particular to preparing diamond- based material usable for manufacture of machining tools. Nano-dispersed diamond particles are subjected to action of predetermined pressures and temperatures, said diamond particles being covered by nanometric graphite or carbon particles, to give diamond-based particles with particle size between 1 and 500 mcm and no more than 2% noncombustible impurities, the latter being optimal for most diamond-containing powder applications. Invention also allows preparation of diamond particles larger than 500 mcm in size. EFFECT: expanded possibilities in manufacture of diamond-based materials. 10 cl, 17 dwg, 5 tbl, 29 ex

Description

 The invention relates to the field of synthesis of superhard materials, in particular to the production of diamond-based material used for the manufacture of a processing tool. The resulting material can be used as a grinding and abrasive material to obtain high-quality surfaces of parts from various materials, in a tool with inserts for drilling, milling and turning of parts, as well as as forming inserts. In particular, the invention relates to a method for processing particles of nanodispersed diamonds.

 Known methods for producing diamond particles of dynamic synthesis (nanodispersed diamonds) [1]. There are two main groups of methods for the dynamic synthesis of diamonds, respectively obtained by detonation and shock-wave compression of carbon-containing substances. In the first case, carbon is in the explosive itself, and in the second, the initial carbon-graphite material is enclosed in an ampoule, which is compressed under the influence of an impact load. Ultrafine diamond (UDD) is obtained mainly by the method of detonation synthesis, although sufficiently dispersed (nanometric) diamonds are also obtained by shock compression using the initial carbon-graphite material with a highly dispersed structure.

 There are also known methods for producing nanodispersed diamond particles by chemical (physical) deposition from a carbon-containing gas (plasma) of atoms, ions, molecules or radicals containing carbon on a substrate when growing a diamond (diamond-like) film [2], pp. 84-108.

 However, this method is extremely expensive, inefficient, time-consuming and is currently used only for scientific purposes.

 Various methods are known for producing synthetic diamonds using blast energy, for example, for producing powders containing diamond particles. In this way get micropowders brand ASMV [3], p.168-171. ASMV micropowders are distinguished by a highly developed surface of diamond particles. Their use during polishing reduces the surface treatment time by 25-30%.

 However, this method of producing diamond particles has the following disadvantages.

 1. To reduce the cost of diamonds, it is necessary to use large explosive charges weighing up to 5 tons. The method involves the use of metal containers (ampoules). The implementation of this method is possible only at large landfills or in underground chambers.

2. When implementing the method, pressures of several tens of GPa and temperatures of 2000-3000 ^° C are used. In this case, to prevent the reverse transition of diamond to graphite due to (due to) high residual temperatures during the explosive synthesis method, various cooling media capable of high speed are used remove heat from synthesized diamond particles.

 3. The extraction of diamond from the synthesis products requires a significant amount of mineral acids, which is associated with both a low diamond yield and the need for sequential removal of the metal cooler, unreacted graphite and various impurities, and then cleaning the surface of the obtained diamond particles. After cleaning, metallic impurities remain in the diamond, worsening its properties.

 4. A feature of diamond powders obtained in this way is the high defectiveness and development of their surface.

 Such powders, as a rule, have a dark, almost black color. Their phase composition is distinguished by the presence, in addition to the cubic, also of the hexagonal phase (lonsdaleite). High development of the surface of diamond particles significantly complicates its chemical cleaning and especially the classification of the powder.

 Other methods are known for producing diamond particles through the use of explosive energy, both due to the production of diamond from various grades of graphite, soot, and the production of diamond from carbon from detonation products of explosives [4], pp. 12-18. The resulting diamond powders have an abrasive ability that is significantly higher in comparison with static synthesis powders [4], p. 14, Fig. 10.

 However, in this case, the synthesis uses high pressures (20-30 GPa), although lower than when implementing the above method (more than 60 GPa). It is also necessary to purify the resulting product from non-diamond carbon and impurities remaining after synthesis.

The high surface energy of such powders is the main obstacle in attempts to obtain homogeneous powders. The high dispersion (2-10 nm) of diamond particles significantly limits their practical use. The detonation synthesis itself is carried out in specialized explosive chambers with a volume of at least 20 m ³ , the inner surface of which must be coated with a corrosion-resistant and impact-resistant alloy.

Однако технология получения и сам материал обладают рядом недостатков.A known method for producing blanks of a composite polycrystalline material containing particles of ultrafine diamond (UDD), described in the description of the invention according to [5]. In this case, a composite polycrystalline material is obtained containing a binder based on refractory compounds of transition metals of groups IV-VI or their eutectic compositions with metals Zn, Cr, Mo, Fe and UDD powder with particle sizes

However, the production technology and the material itself have several disadvantages.

First, the sintering of the material is carried out at a pressure of at least 8.5 GPa and a temperature of at least 1350 ^o C for 5-60 s. Secondly, binder particles and UDD particles differ by several orders of magnitude, namely, 10-100 times, which leads to a decrease in the properties of sintered blanks. Thirdly, the presence in the binder of metals of catalysts that contribute to the sintering of particles and the transformation of the non-diamond form of carbon into diamond reduces the physicomechanical characteristics and heat resistance of the cakes, as well as the cutting properties of the resulting material.

 There is also a method for the synthesis of heat-resistant polycrystals of diamond using non-metallic activating additives, which was proposed in [6], pp. 184-189. As an additive that activates the conversion of graphite -> diamond, boron is selected. It is known that at high temperature boron easily diffuses in graphite and, interacting with carbon, forms boron carbide having a diamond-like structure, the presence of which in the reaction mixture activates the process of diamond formation, acting as a crystallization center.

However, in this case, pressures above 7 GPa and temperatures above 2300 ^° C are used. In this case, the synthesized polycrystals have grain sizes of 3-10 μm and linear dimensions of up to 6 mm, which also limits their use.

 Of the known technical solutions, the closest object to the claimed method for producing diamond particles mainly for the manufacture of diamond-containing material and the material obtained on the basis of nanodispersed diamonds, according to the set of essential features, is a method for producing diamond particles to obtain a material based on diamond, in which nanodispersed diamond particles are subjected to predetermined pressures and temperatures in a carbon-containing medium with graphitization of the surface layer by particle diamonds [7], accepted The author as a prototype.

 Accepted as a prototype method is that they process particles of nanodispersed diamonds of dynamic synthesis (nanodispersed diamonds) by the action of predetermined pressures and temperatures. This gives a material based on nanodispersed diamonds, made in the form of a powder.

The resulting synthetic diamond powder is characterized by an increased (by an order of magnitude) defect density in comparison with static synthesis powders and has the following characteristics:
The particle size, nm - 2-10
Specific surface area S _beats , m ² / g - ≈300-400
The temperature of the onset of oxidation in air, ^o С - ≈400
The temperature of the onset of graphitization in vacuum, ^o С - ≈900
However, the known method has significant disadvantages. The mixture containing diamond particles must be treated with concentrated nitric acid or a mixture of strong mineral acids at temperatures up to 250 ^o C and pressure up to 10 MPa, using special high-pressure equipment made of a corrosion-resistant alloy. Then the diamond particles must be thoroughly washed from acid and dried at elevated temperature.

 The specified processing does not lead to an improvement in structural perfection, does not change the dispersion of particles, but significantly increases manufacturing costs. In addition, the method for producing the diamond-containing charge itself has the following significant disadvantages.

1. High pressures (20-30 GPa) and temperatures (3000-4000 ^o С) are used, which is higher than during shock wave synthesis.

 2. It is necessary to use specialized cameras for synthesis.

 3. A low yield of diamond-containing charge (approximately 10% by weight of explosive), while in the charge the diamond itself is 65-80 wt.%.

 4. A fairly sophisticated technology for cleaning the resulting mixture.

 The synthetic diamond powder obtained by this method has the following disadvantages.

 1. The high dispersion of particles allows their effective use only in a few areas of technology, for example, during superfinishing of materials, as friction modifiers or as adsorbents.

 2. The high specific surface area does not allow to obtain powders of a certain particle size distribution, which is the reason for their low aggregative and sedimentation stability (in liquid media).

 3. The resulting UDD powders are characterized by an increased (by an order of magnitude) defect density in comparison with static synthesis powders.

4. Due to the significant specific surface and structural features, these powders have a high adsorption capacity, which
a) reduces the efficiency of their cleaning and complicates it;
b) it is not possible to effectively use them to obtain polycrystalline superhard materials (in contrast to powders obtained by other methods, in particular by static synthesis).

 As a prototype of the method for producing diamond particles, a method for producing diamond crystals according to the USSR copyright certificate [8], which allows to obtain diamond particles with sizes greater than 500 microns, is adopted.

 When implementing the prototype method, diamond particles are treated by the action of predetermined pressures and temperatures in a carbon-containing medium. In this case, the initial diamond crystal is grown, precipitating on its heated surface the carbon obtained by dissociation of a carbon-containing gas.

 However, this method related to the epitaxial growth of diamond (obtaining synthetic diamonds from the gas phase) has a number of significant drawbacks.

To implement this method, complex equipment and equipment are needed, a significant amount of energy is spent on maintaining the surface temperature of the processed diamond particles (1800-2500 ^o C) and to ensure the dissociation of carbon-containing gas (2300 ^o C). The productivity of this method is very low, which ultimately leads to an increased cost of the resulting product.

 As a prototype of the method for producing diamond-containing preforms, the method described in the patent [10] is selected. A known method for producing preforms containing diamond particles is that they mix diamond powder and a binder material, form preforms from the obtained charge, place an additional layer of silicon over the preform, place the preforms in a container and sinter them at a given pressure.

 In this case, a diamond-containing cake (billet) is obtained in which diamond grains are bonded with silicon carbide.

 However, this known method has the following disadvantages.

 1. Diamond particles sinter at low pressure and for a sufficiently long period of time are exposed to high temperatures, which leads to softening of the diamond, its oxidation and graphitization.

 2. Superhard composite materials based on diamond and cubic boron nitride (CBN), sintered with a binder at normal (reduced) pressure, are inferior in physical and mechanical and other characteristics to similar materials obtained by sintering at elevated pressure, due to the low bond strength between crystals of diamond or CBN.

 3. A rather complicated temperature treatment of diamond, which includes two stages: the first for graphitization of diamond and the second - directly impregnation.

 4. Long-term heat treatment (compared to pressure treatment).

 5. Enough large particles of diamond are processed, which reduces the characteristics of the composite and limits its scope.

The task of the invention is to obtain materials based on diamond with a particle size in the range from 1 to 500 microns and a content of non-combustible impurities of not more than 2 wt.% (Which is optimal for most areas of use of diamond-containing powders), as well as obtaining diamond particles with sizes greater than 500 microns. Moreover, the parameters of the processing process of the initial particles of nanodispersed diamonds are reduced in comparison with the known ones (pressure from 0.133 • 10 ^-10 to 2 GPa, temperature 20-1200 ^o C).

 The objective of the invention is to obtain blanks of diamond-containing materials with a finely dispersed (10-1000 nm) structure, not containing foreign (metallic and non-metallic) inclusions and obtained at relatively low pressures and temperatures for this class of materials.

 As a result of solving this problem, a new technical result was achieved, consisting in increasing the physicomechanical and operational characteristics of diamond-based materials, and in reducing their cost.

 The specified technical result is achieved by the fact that when implementing the method of producing diamond particles mainly for the manufacture of diamond-containing material, in which particles of nanodispersed diamonds are treated by the action of predetermined pressures and temperatures, according to the invention, graphite or carbon, the particle sizes of which are nanometric, are applied to the surface of the diamond particles.

In this case, particles of graphite are applied to the surface of diamond particles by heat treatment of a purified powder of nanodispersed diamonds with graphitization of their surface layer, heating them in vacuum at a temperature of from 1000 to 1500 ^o C.

The graphite layer is increased by additionally precipitating carbon onto the surface of the obtained particles from carbon-containing gas by cooling these particles to a temperature below 300 ^{° C.} and supplying carbon-containing gas to the reaction volume heated to a temperature of from 300 to 1000 ^° C.

In this case, a variant is possible when the surface of the initial diamond particles is moistened with a carbon-containing liquid or carbon-containing groups of carbon-containing gas are deposited on the surface of these particles, heating the gas to a temperature of 300 ^o C and maintaining the temperature of the diamond particles not more than 300 ^o C.

In addition, it is possible to apply graphite to the surface of diamond particles by heat treatment of a crude powder of nanodispersed diamonds with carbon graphitization located on the surface of diamond particles by heating in an inert gas or in vacuum at a temperature of from 1200 to 1500 ^o C, and the carbon layer can be increased by deposition on its surface of carbon from a carbon-containing gas by the above technological method.

In any embodiment of the method for producing diamond particles, a technology is possible when particles of refined nanodispersed diamonds are mixed with nanometer-sized graphite particles, mixed for 2-3 hours, and the resulting mixture is treated at a pressure of 0.133 • 10 ^-10 to 2.0 GPa and temperature from 20 to 1200 ^o With a shutter speed of 10 s to 6 hours in the following ratio of components, wt.%:
Nanodispersed diamond powder with crystallite sizes of 2 - 10 nm - 10 - 50
Nanodispersed diamond powder coated with graphite or carbon - Rest
In this case, particles of graphite or graphite-like boron nitride with sizes not exceeding 1 μm in an amount of from 10 to 50 wt. %, as well as carbon-containing liquid in an amount of from 10 to 100 vol.% of the volume of the obtained mixture.

 It is also possible that up to 10 wt.% Amorphous boron with particle sizes of not more than 1 μm is added to the charge.

 A distinctive feature of the proposed method for producing diamond particles for the manufacture of diamond-containing material is that graphite or carbon, the particle sizes of which are nanometric, are applied to the surface of the diamond particles.

 This allows, firstly, to recrystallize the deposited graphite or carbon into dense carbon modifications in the pressure and temperature range, which is traditionally considered to be the area of thermodynamic stability of "loose" carbon modifications (graphite, soot). Secondly, it contributes to the growth of particle sizes of nanodispersed diamond. Thirdly, it leads to the appearance of sufficiently large diamond particles formed from nanodispersed diamond particles.

 Depending on the structure of the applied carbon, the method of its application and processing conditions, it may be recrystallized into diamond, intermediate hexagonal modifications of carbon, or diamond-like carbon.

 In this case, the powder of nanodispersed diamonds can either initiate the conversion of the introduced graphite (carbon) into dense modifications, or coarsen due to the carbon deposited on their surface with the subsequent fusion of diamond particles inside the aggregates, as well as due to coagulation and coalescence of the aggregates themselves. A mechanism is also possible when individual particles or particle aggregates of nanodispersed diamonds are attached to a larger growing diamond particle.

 Used nanodispersed diamonds, on the one hand, act as an activator and a kind of catalyst for the process of transformation of the initial particles of non-diamond carbon, and, on the other hand, serve as the nuclei of a new diamond phase and its structural elements.

The ability of nanodispersed diamonds to activate the process of diamond formation is related to their structural and surface properties, namely:
- large surface area and high surface energy;
- the presence on the surface of the particles of the functional cover, consisting of chemical compounds of various nature;
- high defectiveness and dispersion of particles;
- the presence of pores of small (nanometric) size in aggregates based on nanodispersed diamonds.

 On the other hand, the possibility of spontaneous transformation of the structure of graphite (non-diamond carbon) under normal conditions is shown, which increases with an increase in its dispersion and structural ordering.

 The experiments performed by the author showed that the structure of highly crystalline graphite after its mechanical grinding (particle size of graphite ranged from units to several tenths of a micron) spontaneously changes over time at atmospheric pressure and room temperature without any additional external influences.

 The transformation is carried out sequentially according to the scheme graphite -> diamond-like carbon.

 The process begins in the most dispersed surface fragments of graphite particles. Studies of the obtained powder have established that, along with graphite, there are particles with a diamond-like structure in the charge, and with increasing exposure time, an increase in the size of such particles occurs.

 It should be noted that the decrease in the energy barrier of the graphite -> diamond-like carbon transition under the above conditions is influenced by the structure of graphite, its dispersion, as well as impurities (for example, iron) that could get into the charge during its mechanical dispersion.

 As a result of the described experiments, colorless (either transparent or turbid) particles based on diamond-like carbon were obtained with sizes from units to several hundred microns (see Figs. 1 and 2). However, the described method for producing diamond-like carbon particles has a significant disadvantage in the duration of the process and the relatively small yield of large particles.

 Thus, graphite (non-diamond carbon) in the bulk state is a stable modification of carbon, and in the dispersed state, after mechanical dispersion, it can be unstable. In this case, the deposition of graphite (non-diamond carbon), especially finely dispersed, on the surface of nanodispersed diamonds additionally thermodynamically and kinetically stimulates the process of diamond formation.

 The driving force that causes phase and structural changes in the nonequilibrium system (nanodispersed diamond - graphite) is its desire to minimize free energy, which causes the transition of "loose" carbon modifications to dense, and also causes the growth of diamond particles at normal and low external pressure . It was also found that non-diamond carbon more easily (from a thermodynamic point of view) passes into diamond if it is in the form of graphite.

Moreover, the graphitization of the surface layer of diamond particles is carried out by heating in vacuum at a temperature of from 1000 to 1500 ^o C. The experiments performed by the author showed that temperatures less than 1000 ^o C are insufficient for graphitization of the surface layer of nanodispersed diamonds, and heating to a temperature of more than 1500 ^o C impractical for economic reasons, since it does not accelerate the process of graphitization of the surface layer of diamond particles and can lead to complete graphitization of diamond.

The need to heat the mixture in vacuum is due to the fact that in the presence of oxidizing agents in the specified temperature range, diamond combustion (oxidation) occurs with the formation of CO ₂ .

In addition, a distinctive feature is that the graphite layer can be increased by additionally depositing carbon on the surface of the obtained particles from a carbon-containing gas by cooling these particles to a temperature below 300 ^o C and supplying carbon-containing gas heated to a temperature from 300 to 1000 to the reaction volume ^o C. For this, the reaction volume is cooled after the first stage of graphitization, and the carbon-containing gas is heated to the indicated temperature before being fed into the reaction volume. In this case, the carbon-containing gas decomposes, releasing free carbon, and the latter is sorbed onto a graphite layer formed on diamond particles during the first stage of graphitization.

These features allow
- minimize the amount of impurities in the resulting diamond particles;
- increase the contact area of nanodispersed particles of diamonds and graphite, as well as create conditions for coherent intergrowth at the boundary of the diamond particle - graphite particle;
- to provide direct contact between the diamond surface and graphite, which increases the likelihood of diamond nucleation due to the significant influence of the surface forces of the seed crystals of nanodispersed diamonds on the formation of a new phase (auto-epitaxy);
- to ensure uniform distribution of graphite in the mixture;
- to ensure a consistent orientation of graphite within the applied layer;
- to save residual internal planar deformation of graphite (contributes to the corrugation of graphite);
- to obtain fine (ultrafine) graphite, unstable thermodynamically and having a large surface area, high surface energy, distorted crystal lattice;
- intensify diffusion processes due to the presence of stresses at the diamond - graphite interface;
- eliminate the formation of stable intermediate diamond-like carbon modifications after the end of the processing of the material;
- additionally affect graphite by forces arising from the small size of the particles used and the presence in the aggregates of pores of small radius (nanoporosity);
- to obtain larger diamond particles due to coagulation and coalescence of the initial graphitized aggregates from nanodispersed diamonds (crystallization from a colloidal state);
- to regulate a layer of graphite (non-diamond carbon) on the surface of diamond particles with additional deposition of carbon from a carbon-containing gas.

Another distinctive feature of the proposed method for producing diamond particles is that the surface of the initial diamond particles is moistened with a carbon-containing liquid or carbon-containing groups of carbon-containing gas are deposited on the surface of these particles, heating the gas to a temperature of 300 to 1000 ^o C and maintaining the temperature of the diamond particles not more than 300 ^o C.

 This allows additional free carbon to be obtained as a result of decomposition of the deposited surface carbon-containing compounds during subsequent heat treatment.

 The indicated temperatures of the diamond particles and the carbon-containing gas are determined by the processes described above.

A distinctive feature of the proposed method for producing diamond particles is that a variant is possible in which graphite is applied to the surface of diamond particles by heat treatment of a crude powder of nanodispersed diamonds with graphitization of carbon located on the surface of diamond particles by heating in vacuum at a temperature of from 1200 to 1500 ^o C, while the carbon layer can be increased by deposition on its surface of carbon from a carbon-containing gas as described above.

When heated to a temperature of less than 1200 ^{° C.} , a sufficient amount of graphite does not form on the surface of diamond particles. When the heating temperature rises to more than 1500 ^o C, energy consumption increases without accelerating the graphitization of the surface layer of diamond particles, which leads to an increase in the cost of the final product, and complete graphitization of diamond can occur.

 The need for the indicated process of graphitization in vacuum is justified above.

The considered distinctive feature allows
- not to clean pre-used nanometric diamonds from non-diamond carbon, which reduces the cost of the initial charge;
- get a given layer of graphite on the surface of the diamond.

Another distinctive feature of the proposed method for producing diamond particles is that they mix particles of refined nanodispersed diamonds with graphite particles of nanometric size, mix for 2-3 hours, and the processing of the resulting mixture is carried out at a pressure of from 0.133 • 10 ^-10 to 2.0 GPa and a temperature of from 800 to 1200 ^o With a shutter speed of 10 to 60 s in the following ratio of the components of the mixture, wt.%:
Nanodispersed diamond powder with crystallite sizes of 2 - 10 nm - 10 - 50
Nanodispersed diamonds coated with graphite or carbon - Rest
Moreover, particles of graphite or graphite-like boron nitride with sizes of not more than 1 μm in an amount of from 10 to 50 wt.%, As well as a carbon-containing liquid in an amount of from 10 to 100 vol.% Of the volume of the obtained mixture, can be added to the charge.

 In addition, in any case, up to 10 wt.% Of amorphous boron with a particle size of not more than 1 μm can be added to the mixture.

 These distinctive features cause the following characteristic positive properties of the process.

 Additives of refined nanodispersed diamonds in the charge accelerate the process of diamond formation. Moreover, the addition of these diamonds in an amount of less than 10 wt.%, As shown by experiments, does not lead to a significant increase in the yield of diamonds, and the addition of more than 50 wt.% Leads to an unjustified increase in the cost of the charge.

 Mixing the mixture contributes to the uniform distribution of its components. Moreover, it was experimentally established that when mixing for less than 2 hours, the effect of the addition of refined nanodispersed diamonds decreases as a result of uneven distribution in the charge, and mixing for more than 3 hours becomes unprofitable, since it does not lead to an increase in the number of synthesized diamonds and the synthesis of more large particles, but only increases the cost of the process.

 The limits of the technological parameters of processing the resulting mixture are also established experimentally.

 The processing of the mixture at low (atmospheric and low) pressures and low temperatures significantly simplifies the technology for producing diamond particles, eliminates the need for complex equipment.

At a pressure of less than 0.133 • 10 ^-10 GPa, an increase in the yield of the product is not observed, and the costs of creating a vacuum increase sharply.

 The increase in pressure reduces the temperature and processing time of the mixture, increases the yield of the product. However, an increase in pressure to above 2.0 GPa is impractical due to the complexity and increase in the cost of the equipment used.

When the processing temperature is less than 800 ^o With there is no increase in the yield of synthesized particles, this temperature is normal for workrooms and its artificial reduction is impractical.

Heating the charge accelerates the process of diamond formation, however, at temperatures above 1200 ^o C, the cost of maintaining the temperature increases, and a significant increase in the yield of the final product is not observed, which leads to an increase in the cost of the resulting synthetic diamonds.

 Exposure of less than 30 s after mixing is technically difficult and impractical, and exposure of more than 60 s does not lead to any changes in the resulting product and only lengthens the processing cycle.

 The addition of graphite particles with sizes not exceeding 1 μm in an amount of from 10 to 50 wt. % allows you to replace part of the nanodispersed diamonds, which leads to a decrease in the cost of the initial charge. As a result of mixing, graphite (as a less solid component of the mixture) is deposited on the surface of nanodispersed diamonds and the formation of a uniform (in volume) charge (homogenization). When using graphite particles with sizes larger than 1 μm, the synthesis process proceeds with lower intensity due to the higher stability of graphite in particles of this volume and because of the smaller contact area of graphite particles and nanodispersed diamonds. With graphite particle sizes above 1 μm, it is necessary to increase the pressure and temperature of the process and use metal catalysts that dissolve graphite.

 In addition, when using large particles of graphite, the formation of cubic diamond is difficult. After synthesis, the formation of diamond-like hexagonal modifications is predominantly fixed. In this case, the formation of cubic diamond is also possible, which is formed during the transformation of intermediate phases in the process of particle growth. However, this requires a long exposure, which is not economically feasible.

 When a small amount of graphite is added (less than 10 wt.%), The effect of replacing part of the nanodispersed diamonds is negligible, and when more than 50 wt.% Of graphite is added after synthesis, unreacted graphite remains.

Graphite and graphite-like boron nitride (BN _G ) have an isoelectronic structure, have a similar structure and close thermodynamic characteristics. Studies have shown that in the nanodispersed diamond - BN _{G system} , dense modifications of boron nitride are synthesized under the same conditions as the formation of dense carbon-based modifications in the nanodispersed diamond - graphite (carbon) system. Moreover, cubic boron nitride (BN _K ), wurtzite boron nitride (BN _B ) and graphite-like boron nitride (BN _G ) are fixed in the synthesis products. The sequence of transition of BN _Г into dense modifications is as follows: the initial graphite-like boron nitride (BN _Г ) is amorphized, then partially goes into a wurtzite modification, then a transition to a cubic modification occurs.

As a result of contacting the surface of nanodispersed diamonds with boron nitride particles under the above conditions, disordering of the initial BN _G is observed, then cubic boron nitride BN _{K is formed} , and a small amount of wurtzite boron nitride is observed in the charge. As in the case with graphite, the use of initial boron nitride particles smaller than 1 μm in size makes it possible to intensify the process of converting BN _G into dense modifications, which, by analogy with graphite, indicates a decrease in the stability of BN _G with an increase in its dispersion.

When using less than 10 wt.% BN _G in the charge, a very small yield of dense phases is obtained, which reduces the efficiency of the process, and when BN _G additives exceed 50 wt.%, Unreacted BN _G remains in the resulting product.

Additives of boron with particle sizes less than 1 μm into the charge with graphite (carbon) with nanometric particle sizes cause the formation of boron carbide B ₄ C, the formation of which increases with increasing temperature of the processing of the charge. The presence of B ₄ C stimulates the process of diamond formation. However, when amorphous boron additives exceed 10 wt.%, The efficiency of the process is reduced. Firstly, the amount of boron reacting with carbon decreases (relatively), and secondly, an increase in the fraction of boron carbide, which serves as crystallization centers, increases the number of such centers, which leads to a decrease in the optimal size of the formed diamond particles .

Processing a mixture based on nanodispersed diamond - graphite (carbon) with a carbon-containing liquid allows
- additionally obtain carbon, which is formed as a result of decomposition by heating carbon-containing groups;
- intensify the mass transfer of carbon (including the particles of nanodispersed diamonds themselves);
- reduce friction between particles;
- to facilitate coagulation of the initial particles of the mixture, which increases the size of the synthesized diamond particles, especially when processing the mixture directly in the liquid).

 With the addition of carbon-containing liquid of less than 10 vol.% (Of the charge volume), the effect of its use is practically not observed (the amount and dispersion of synthesized diamond particles practically do not differ from the particles obtained by using a dry charge), and the addition of carbon-containing liquid is more than 100 vol. % does not lead to an increase in the yield (amount, size) of synthesized diamond particles and affects the energy performance of the process.

 The specified technical result is also achieved by the fact that in the implementation of the method for producing diamond particles, in which diamond particles are treated by the action of predetermined pressures and temperatures in a carbon-containing medium, nanodispersed diamonds are used as diamond particles, with graphite being applied to the surface of these particles or carbon, the particle sizes of which are nanometric, and after obtaining the final product, the latter is classified by separating diamond particles with sizes from 1 to 500 microns.

 A distinctive feature of the method for producing diamond particles is that nanodispersed diamonds are used as diamond particles, while graphite or carbon is applied to the surface of these particles, the particle sizes of which are nanometric, and after the final product is obtained, the latter is classified by separating diamond particles with sizes greater than 500 microns.

 The use of nanodispersed diamonds as diamond particles when applying to the surface of these particles graphite or non-diamond carbon, the particle sizes of which are made nanometric, can significantly reduce the cost of the technological process in comparison with the prototype. As follows from the above methods for producing diamond particles from nanodispersed diamonds coated with graphite or carbon on their surface, the process parameters (pressure and temperature) are significantly lower than those of traditional technological processes for producing synthetic diamonds, which reduces the cost of the equipment used and reduces operating costs .

 The separation of diamond particles with sizes greater than 500 microns after obtaining the final product by known classification methods allows to obtain two useful products: powder used as an abrasive material, and large particles (more than 500 microns) of diamond used as an insert for a cutting tool. It should be noted that the quality of the crystal structure of the obtained large diamond particles allows them to be used for jewelry purposes. Thus, when producing diamond particles by the claimed method, there is no waste, and large particles of diamond are of increased value in comparison with the same synthetic diamonds made by other known methods.

The specified technical result is also achieved by the fact that in the implementation of the method for producing diamond-containing preforms, in which diamond powder and binder material are mixed, preforms are formed from the obtained charge, the preforms are placed in a container and treated with elevated pressure, according to the invention, nanodispersed diamond powder with dimensions crystallites from 2 to 10 nm, and the same powder is used as a binder material, on the surface of the particles of which graphite or carbon is applied, and the batch is sintered at a pressure of from 2.5 to 4.0 GPa and a temperature of from 800 to 1200 ^o C with a holding time of 10 to 60 s, while obtaining blanks with a density of 0.5-0.9 of the density of diamond, with the ratio of the components %:
Nanodispersed diamond powder with crystallite sizes of 2 - 10 nm - 40-60
Powder of nanodispersed diamonds, on the surface of the particles of which carbon is deposited - Rest
In this case, carbon-containing groups of carbon-containing gas can be additionally deposited onto the surface of the batch particles by heating the gas to a temperature of from 300 to 1000 ^{° C.} or by wetting the batch with a carbon-containing liquid.

 When implementing the described method for producing diamond-containing preforms, the obtained preforms can be crushed to particles with a size of from 0.01 to 0.5 mm. It is also possible to use the mixture obtained by this method as a binder in the manufacture of composite superhard materials.

A distinctive feature of the proposed method for producing preforms containing diamond particles is the use of nanodispersed diamond powder with crystallite sizes from 2 to 10 im, and the same powder is used as a binder material, the surface of the particles of which is coated with graphite or carbon, and the resulting mixture is sintered at pressure from 2.5 to 4.0 GPa and a temperature of from 800 to 1200 ^o With a shutter speed of from 10 to 60 s, while receiving blanks with a density of 0.5-0.9 of the density of the diamond.

 This feature makes it possible to obtain blanks based on nanodispersed diamonds, and nanodispersed diamond particles coated with graphite or non-diamond carbon are used as a binder. Particles of nanodispersed diamond coated with graphite (carbon) act as a carrier of non-diamond carbon, which contributes to the dispersion of non-diamond forms of carbon and their recrystallization into dense modifications. In this case, heat treatment accelerates the recrystallization of graphite (carbon), which is also in a finely dispersed state, into diamond (diamond-like carbon) and promotes the sintering of particles of the workpiece material at low compaction parameters.

 The use of nanodispersed diamond powders with crystallite sizes of less than 2 nm for the method for producing diamond blanks containing diamond particles is impractical due to the difficulty of producing such powders (it is necessary to develop new, currently absent technologies for producing nanodispersed diamonds with sizes less than 2 nm). It is also inexpedient to use nanodispersed diamond powders with particle sizes of more than 10 nm for the method of producing preforms due to a decrease in their activity with increasing sizes to more than 10 nm, which reduces the efficiency of the method.

 The processing parameters of the mixture are established experimentally.

 At a pressure of less than 2.5 GPa, the quality of the resulting workpieces deteriorates due to insufficient compaction.

 At a pressure of more than 4.0 GPa, costs increase and the cost of billets increases.

When the processing temperature is less than 800 ^o With the necessary processing time of the mixture increases, the quality of the workpiece material is deteriorated due to sintering defects.

At a temperature of more than 1200 ^o C increases the cost of the workpieces, there is a risk of loss of the final quality of the material due to the effect of graphitization of diamond particles.

 Exposure less than 10 s is difficult to implement technologically and impractical.

 Exposure to more than 60 s leads to an increase in costs without a noticeable increase in the properties of the resulting workpiece material.

 Using the described technological methods, the density of the workpiece, as established experimentally, is obtained in the range of 0.5-0.9 of the density of the diamond. It is impractical to obtain a lower density, and a higher density cannot be achieved due to limitations imposed by other parameters of the proposed method.

A distinctive feature of the inventive method for producing preforms containing diamond particles is also that carbon-containing groups of carbon-containing gas can be additionally deposited onto the surface of the batch particles by heating the gas to a temperature of 300 to 1000 ^° C or wetting the batch with a carbon-containing liquid.

 The deposition of carbon-containing groups on the surface of nanodispersed diamonds contributes to additional diamond formation during the subsequent heat treatment, as described above when considering a method for producing diamond particles. Diamond particles synthesized from carbon from surface carbon-containing groups are formed mainly in the pores of the resulting workpiece, which helps to increase the physicochemical properties of the workpiece.

 An additional distinctive feature of the method for producing diamond-containing preforms is that a variant is possible in which the obtained preforms are crushed to particles ranging in size from 0.01 to 0.5 mm.

 Subsequent grinding of the sintered preforms makes it possible to obtain a diamond powder with a polycrystalline structure and particle size within the claimed limits for using the resulting powder as an abrasive material.

 Another distinctive feature of the method for producing preforms containing diamond particles is that a variant is possible in which the resulting charge is used as a binder in the manufacture of composite superhard materials.

 Using the inventive charge as a binder allows one to obtain polycrystalline superhard materials (PSTM) on the basis of a sufficiently wide range of other large powders of superhard materials (STM), and the granularity of the powders of the latter can be up to several hundred microns. In the process of sintering, the mixture forms a nanocrystalline bond connecting the larger grains of STM. The use of a binder based on nanodispersed diamond powders increases the physicomechanical properties of composite materials, and also allows to lower the sintering temperature and time, not to use catalysts and foreign binders, but to use only carbon. All this allows us to expand the technological range of the products obtained, to expand their area of use.

 The indicated technical result is also achieved by the fact that a material based on nanodispersed diamonds is obtained, which is used as an insert for a cutting or shaping tool and made by sintering a mixture containing diamond particles, in which according to the invention nanodispersed diamond powder is used, in which the particle size increased to values from 10 to 1000 nm, the density of the material of the insert is made from 0.5-1.0 of the density of diamond, the hardness of the material is made not less than 60 GPa with the amount non-combustible impurities from 1 to 2%.

 A distinctive feature of the obtained material is that nanodispersed diamond powder is used as diamond particles, in which the particle size is increased to 10 to 1000 nm, the density of the insert material is made from 0.5-1.0 of the density of the diamond, the hardness of the material is not less than 60 GPa with the amount of non-combustible impurities from 1 to 2%.

This allows
- abandon the additives of catalysts and binders during sintering and the preparation of blanks;
- receive billets with a grain size of up to 1 μm (nanomaterial), which provides high quality processing, including hard materials;
- receive billets with high physical and mechanical properties and heat resistance, with a minimum amount of impurities;
- use the resulting nanomaterial as a binder for larger CTM grains, in particular diamond, i.e. larger in comparison with nanodispersed diamond, as described above, when using workpieces containing diamond particles manufactured by the production method, followed by grinding them;
- reduce pressure, temperature, sintering time, reduce the cost of the material.

The specified technical result is also achieved by the fact that when implementing the method for producing preforms containing diamond particles, in which diamond powder and binder material are mixed, preforms are formed from the obtained charge, an additional silicon layer is placed over the preform, the preforms are placed in the container and sintered at a given pressure, according to the invention, diamond powder of nanodispersed diamonds with crystallite sizes from 2 to 10 nm is used, and the same powder is used as a binder material, the particle size of which is coated with graphite or carbon, and the resulting mixture is sintered at a pressure of from 2.5 to 4.0 GPa and a temperature of from 1400 to 1600 ^° C with a holding time of 10 to 60 s, whereby blanks with a density of 0.8-1 are obtained, 0 of the density of diamond.

 In this case, it is possible to use the starting material used for implementing this method as a binder in the manufacture of composite superhard materials.

A distinctive feature of the inventive method for producing preforms containing diamond particles is that they use diamond powder of nanodispersed diamonds with crystallite sizes from 2 to 10 nm, and use the same powder as a binder material, the surface of the particles of which is coated with graphite or carbon, and the resulting mixture is sintered at a pressure of from 2.5 to 4.0 GPa and a temperature of from 1400 to 1600 ^o With a shutter speed of from 10 to 60 s, while receiving blanks with a density of 0.8-1.0 of the density of the diamond.

 These distinctive features make it possible to combine the processes of recrystallization of graphite (carbon) into diamond (diamond-like carbon) with the processes of sintering of nanodispersed diamonds and the impregnation of the formed workpiece with molten silicon with the formation of silicon carbide.

 These distinctive features of the method for producing blanks containing diamond particles allow silicon to be impregnated with the inventive charge together with large particles of superhard material, in particular diamond. As a result, porosity is eliminated and the workpiece is hardened by silicon carbide.

In addition, it allows
- intensify the process of impregnation along the boundaries of large diamond grains;
- bind large diamond grains with a nanocrystalline bond reinforced with silicon carbide.

 This, in turn, increases the strength properties of composite materials due to the absence of pores, hardening by silicon carbide, a stronger bond between diamond particles, and also simplifies the manufacturing technology of the material compared to traditional methods.

 In addition, a distinctive feature of this method of obtaining preforms containing diamond particles is that it is possible to use the starting material used for implementing this method as a binder in the manufacture of composite superhard materials.

 This distinctive feature makes it possible to use all the advantages of the technological process described above for implementing the method for producing preforms containing diamond particles in the manufacture of composite superhard materials based on other components of the composite.

 Thus, the claimed invention allows to increase the physico-mechanical and operational characteristics of the obtained materials based on diamond, to reduce their cost.

 Figure 1 presents a separate particle based on diamond-like carbon obtained on the basis of graphite particles with nanometric dimensions after mechanical dispersion and subsequent exposure at atmospheric pressure and room temperature (scale: 1 cm - 100 microns, magnification 100x).

 Figure 2 presents the flake with the fibers formed on its surface in the conditions of figure 1 (scale: 1 cm - 50 μm, magnification 200x).

 Figure 3 presents the result of the synthesis according to the method for producing diamond particles, consisting of particles of diamond and diamond-like carbon (scale: 1 cm - 100 μm, magnification 100x).

 Figure 4 presents the individual diamond particles obtained by processing the mixture according to the method of producing diamond particles with preliminary graphitization of the surface of the purified particles of nanodispersed diamonds (scale: 1 cm - 25 μm, magnification 400x).

 In FIG. Figure 5 shows the obtained material after processing the mixture with the modification of the initial powder by the deposition of carbon-containing groups on the surface of its particles from the gas phase or from the liquid (scale: 1 cm - 50 μm, magnification 200x). Large particles (50-100 microns) and smaller ones (less than 50 microns) are visible.

 Figure 6 shows the diamond particles obtained by mixing graphitized particles and purified particles of nanodispersed diamonds, followed by heat treatment of the resulting mixture in vacuum (scale: 1 cm - 30 μm, magnification 33x).

 Figure 7 presents the diamond particles obtained as a result of additional ultrasonic and subsequent vacuum processing of the charge (scale: 1 cm - 100 μm, magnification 100x).

 On Fig presents a diamond particle (spherical) obtained by ultrasonic treatment of the mixture in a liquid (scale: 1 cm - 50 microns, magnification 200x).

 In FIG. 9 shows a large diamond particle obtained by processing the charge according to the claimed method for producing diamond particles, including classification (sieving) of the obtained product (scale: 1 cm-100 μm, magnification 100x), Particle sizes: large diagonal 750 μm, smaller 550 μm .

 In FIG. 10 shows the microstructure of a material based on nanodispersed diamond obtained by the method for producing preforms containing diamond particles (scale: 1 cm - 100 μm, magnification 100x).

 In FIG. 11 is an electron micrograph of a diamond billet material obtained by a method for producing billet containing diamond particles (scale: 0.7 cm, 1 cm, magnification 14300x).

 On Fig presents a spherical diamond particle obtained on the basis of the inventive material (scale: 1 cm - 1.5 microns, an increase of 6600x).

 On Fig presents a diamond particle in the form of a fiber, obtained on the basis of the inventive material (scale: 1 cm - 7 microns, magnification 7150x).

 On Fig presents a diamond particle in the form of flakes obtained on the basis of the inventive material (scale: 1 cm - 7 microns, magnification 7150x).

 On Fig presents a round diamond particle obtained on the basis of the inventive material (scale: 1 cm - 1.5 microns, an increase of 6600x).

 In FIG. 16 shows a diamond particle with a facet obtained on the basis of the inventive material (scale: 1 cm - 3 μm, magnification 3300x).

 On Fig presents diamond particles with particle sizes up to 500 microns, obtained by the present method for producing diamond particles (scale: 1 cm - 200 microns, magnification 50x).

 The essence of the invention is illustrated by the following examples.

 Example 1

 50 wt.% Nanodispersed diamonds and 50 wt.% Graphite were mixed with particle sizes in the nanometric range (less than 1 μm). Mixed in a mixer for 2-3 hours. As a result of mixing, graphite particles were deposited on the surface of nanodispersed diamonds in the form of aggregates (conglomerates).

The resulting mixture was placed in a vacuum oven, heated to a temperature of 500-1200 ^o C, kept at this temperature for 10-30 minutes and then cooled.

 The result was a mixture containing a diamond of cubic modification and diamond-like carbon (see figure 3). Graphite in the mixture after sintering was practically not detected.

When using less than 10 wt.% Nanodispersed diamonds, unreacted carbon (graphite) remains, using more than 50 wt.% Is not economically feasible. When using large particles of graphite (more than 1 μm), the process of applying it to diamond particles is difficult (the contact surface is smaller), the process of graphite transformation is difficult (unreacted graphite remains). When mixed for less than 2 hours, the result is worse. Mixing more than 3 hours is not economically feasible. When heated in a vacuum to 500 ^o C, a large exposure time is required, unreacted graphite remains. Heating in vacuum to more than 1200 ^o With economically impractical. When holding for less than 10 min, graphite remains, it is technologically difficult to implement this mode. Exposure for more than 30 minutes is not economically feasible.

 Example 2

The purified powder of nanodispersed diamonds was taken, their surface was graphitized by holding in vacuum (τ ~ 10-30 min, T ~ 1000-1500 ^o С). Then the same powder was subjected to vacuum treatment again (τ ~ 10-30 min) at Т ~ 500-1200 ^o С.

 The result was a diamond powder with enlarged (more than 10 nm) compared with the original particles (see figure 4).

 Shorter exposure time and lower temperatures during graphitization lead to insufficient graphitization, therefore, subsequent diamond formation is worse. Large τ and T are not economically feasible to use.

 Example 3

 They took the purified nanodispersed diamond powder, carried out their surface graphitization in an inert gas medium, the modes are similar to those in example 2. The heat treatment was performed a second time (modes according to example 2) in vacuum. Received a diamond powder with enlarged (relative to the source) particles of the same size as in example 2 (see figure 4).

 Example 4

 As the initial powder used powder of nanodispersed diamonds with a graphitized surface obtained in example 2 or 3.

The powder was placed in a reactor at a temperature of not more than 300 ^° C. The carbon-containing gas (CO) was then fed into the reactor, which was preheated to T = 300–1000 ^° C. At a gas heating temperature of less than 300 ^{° C., the} process took a long time ( uneconomical). At a gas heating temperature of more than 1000 ^o C there is intense wear of equipment (uneconomical).

As a result of the decomposition of carbon monoxide by the reaction 2CO = C + CO _2, free carbon was deposited on the surface of the powder particles.

 The process of growing the initial graphite layer was carried out to a diamond / graphite mass ratio of from 1: 1 to 1:10, determined by weighing the powder before and after the process.

 When the ratio of the masses of diamond and graphite is less than 1: 1, subsequent diamond formation proceeds non-intensively (smaller particles are formed), when the ratio of diamond and graphite above 1:10, the process of diamond formation is difficult, and the cost of production increases.

 The secondary processing of the powder was carried out similarly to the above examples 1-3. Received a diamond powder with enlarged (relative to the source) particles of the same as in example 2 or 3 (see figure 4).

 Example 5

 The nanodispersed diamond powder was taken with graphite or carbon deposited on the surface of the diamond particles.

 The powder was wetted with a carbon-containing liquid by immersion in it the original powder. As the carbon-containing liquid, alcohol, acetone, etc., that is, compounds containing carbon and suitable for the synthesis of diamond, are selected. After wetting, the powder was removed from the liquid and dried. As a result, a powder was obtained whose surface contains (as a result of adsorption) molecules of a carbon-containing liquid.

 Another way to modify the surface of the starting powder is to deposit carbon-containing groups from the gas phase on the surface of the powder. Gas-phase modification was carried out analogously to example 4. As carbon-containing gases, hydrocarbons or other compounds containing carbon and suitable for the synthesis of diamond can be used. The quality of the powder treatment was checked experimentally (by the yield of diamond).

Then, the resulting mixture was re-treated in the same way as in examples 1-4, heated in vacuum to T ~ 500-1200 ^o C.

 Received a diamond powder with enlarged (relative to the source) particles (see figure 5).

 Example 6

 They took the powder of crude nanodispersed diamonds coated with a non-diamond carbon layer having a carbon black structure obtained by other known methods, for example, by the detonation method [4].

The powder was placed in a reactor and heated at a temperature of from 1200 to 1500 ^o With in vacuum. Exposure was carried out from 30 to 60 minutes

With a holding time of less than 30 minutes, insufficient graphitization of surface non-diamond carbon was noted. A time greater than 60 minutes is not economically feasible. At temperatures below 1200 ^o C - insufficient graphitization of surface non-diamond carbon. A temperature of more than 1500 ^o With economically impractical.

 As a result of heat treatment, ordering (graphitization) of non-diamond carbon occurs. The quality of the obtained powder was determined experimentally.

 Secondary heat treatment was carried out in accordance with examples 1-5.

 As a result of the 2nd treatment, diamond particles with a size larger than the original were obtained (see Figs. 4 and 5).

 Example 7

 A nanodispersed diamond powder prepared according to the first stage of Example 6 was taken with graphite on the surface. The powder was placed in a reactor, then carbon monoxide (CO) was supplied. Heat treatment and the duration of the process was carried out analogously to example 4.

 Then, a secondary heat treatment was carried out - according to examples 1-6. After secondary processing, a diamond powder with larger particles was obtained (see FIGS. 4 and 5).

 Example 8

The powder treated according to any one of examples 2-7 was taken to graphitize the surface of the nanodispersed diamond particles, mixed with the purified nanodispersed diamond powder, and mixed for 2-3 hours in a mixer. The resulting mixture was placed in a vacuum oven. Heat treatment was carried out at a residual pressure of 0.133 • 10 ^-10 GPa. Processing temperature: T _arr ~ 500-1200 ^o C. Processing time 30 min. The oven was cooled to room temperature (within 6 hours). The result was a diamond powder with larger particles relative to the initial nanodispersed powders (see Fig.6).

 The experimental options for the processing parameters of the mixture according to example 8 and the resulting results are shown in table 1.

When the pressure in the vacuum furnace is more than 10 ^-1 mm RT.article powder oxidation is also observed due to the presence of residual oxygen.

 Example 9

The mixture was prepared in accordance with Example 8. The resulting mixture was treated with a pressure of 2 GPa at τ = 60 s and T = 500 ^° C. After depressurization, a powder was obtained with enlarged particles (compared to the initial powder). With the specified processing parameters, sintering of the mixture into the workpiece does not occur. The results of other experiments are shown in table 2.

 With the addition of purified nanosized powder of 10-50 wt.%, The effects are the same as in example 8.

 Example 10

To prepare the mixture, the initial components were taken in the following amount (wt.%):
- a powder prepared according to any one of the embodiments of the first method for producing diamond particles, 50;
- powder refined nanodispersed diamonds 10;
- graphite powder with a particle size of less than 1 μm 40.

 The mixture was stirred in the mixer for 2-3 hours, after which the mixture was subjected to heat treatment in vacuum in accordance with the modes described in example 8.

 As a result of heat treatment of the charge, diamond particles formed larger than the initial ones and diamond-like carbon particles.

 Experimental options for the processing parameters of the mixture according to example 10 and the resulting results are shown in table 3.

 Example 11

To prepare the mixture, the initial components were taken in the following amount, wt.%:
- a powder prepared according to any one of the embodiments of the first method for producing diamond particles, 10;
- powder of refined nanodispersed diamonds 40;
- powder of graphite-like boron nitride with a particle size of less than 1 μm 50.

 Preparation and sintering - in accordance with example 10.

 As a result of heat treatment of the charge, particles of diamond and cubic boron nitride were found in the synthesis products.

 The experimental options for the processing parameters of the mixture according to example 11 and the resulting results are shown in table 4.

 Example 12

 The mixture was prepared in the composition: graphite, nanodispersed diamond powder (refined and unrefined) in the ratio described in example 10. The mixture was mixed (examples 8, 9, 10, 11), then subjected to pressure treatment (according to example 9). As a result, particles of diamond, diamond-like carbon, were obtained (see FIG. 6).

 Example 13

 The mixture was prepared according to example 11 with boron nitride. Then subjected to pressure treatment (examples 9, 12).

 As a result, particles of diamond, cubic boron nitride, the powder of which is an analogue of a powder of diamond particles and diamond-like carbon, were obtained (see FIG. 3).

 Example 14

 The mixture was prepared according to examples 8, 9, 10, 12. A carbon-containing liquid was introduced into the mixture based on compounds suitable for the synthesis of diamond (for example, alcohol or glycerin) in an amount of 50 vol% of the charge volume. Next, the mixture was processed according to examples 8, 9, 10, 11, 12, 13. As a result of processing, particles of diamond and diamond-like carbon were obtained (see FIG. 3).

 With the introduction of a liquid of less than 10 vol.%, The effect is negligible, since there is no increase in the yield of the product.

 Example 15

 The charge was taken according to examples 8, 9 10, 12, 14, 5 wt.% Boron (amorphous) with a particle size of less than 1 μm was added. Stirred for 2-3 hours. The charge was processed by any method described in examples 8-14.

 As a result, the yield of larger diamond particles was increased as in Example 15 (see FIG. 6).

 With the addition of boron in excess of 10 wt.%, The effect of using a boron additive is reduced.

 Example 16

 They took the mixture obtained according to any of the previously considered options for the preparation of the mixture in examples 1-10, 12, 14-15, subjected the mixture to processing the specified pressure and temperature (any option given in examples 1-10, 12, 14-15). After processing, the product was classified (sieve method).

 As a result, diamond particles with a size of more than 500 μm were isolated (the maximum particle size of the resulting particles was 1 mm) (see Fig. 9).

 Example 17

 We took 40 wt.% Powder of refined nanodispersed diamonds and 60 wt.% Nanodispersed diamonds with graphite (carbon) deposited on the surface. They were placed in a mixer and thoroughly mixed for 2-3 hours.

Billets of the required dimensions (diameter 5-10 mm, height 5 mm) were pressed from the obtained mixture by pressing in a mold under a pressure of 300-500 MPa. Then the blanks were placed in a container of lithographic stone (dolomite), which was then installed in a high-pressure apparatus. Then, the sintering of the mixture was carried out under a pressure of 3.5 GPa and a temperature of 1100 ^o C for 30 s. After sintering, the pressure and temperature were reduced to the initial values and the preform was removed, which is a polycrystalline sinter, which after machining can serve as a working element in a blade tool or for the manufacture of diamond dies (see Fig. 10). Other examples of obtaining diamond blanks are shown in table 5.

 With a decrease in the fraction of refined nanodispersed diamonds in the charge (less than 30 wt.%), The properties of the workpieces are deteriorated (microhardness and density are reduced). With an increase in the proportion of refined powder (more than 70 wt.%), The properties of the workpieces are deteriorating (reduction in microhardness), and the cost is increasing. When P, T, τ is less than those indicated, a decrease in the properties of the workpieces is observed. At T, τ above the properties of the workpieces deteriorate. When P above the above increases the cost.

 Example 18

 We took 50 wt. % powder of refined nanodispersed diamonds with graphite (carbon) on the surface. The mixture was prepared according to example 17. Next, the surface of the mixture was modified with carbon-containing chemical compounds (according to example 5).

 After that, the initial billet was pressed and its temperature treated under pressure (Example 17). After processing, a preform was removed, which was a polycrystalline diamond cake (see Fig. 10).

 As a result of applying carbon-containing compounds to the surface of the charge, the quality of the diamond billet increased, its porosity decreased due to the formation of diamonds in the pores, which in this case performed the functions of a special filler - silicon used in the implementation of the method for producing billets containing diamond particles (see Fig. 11) .

 Processing modes, the composition of the mixture used were the same as those shown in table 5 for example 18.

 Example 19

 A preform was obtained according to any one of examples 16, 17. The preform was mechanically ground (crushed) to obtain a powder, after which the resulting powder was sieved through a sieve system, fractions of powder particles in the range from 0.01 to 0.5 mm were isolated. In this case, a powder was obtained that can be used in the same areas as that obtained by the method of producing diamond particles: as a grinding and abrasive material to obtain high-quality surfaces of parts (see Fig. 17).

 Example 20

A mixture was prepared on the basis of nanodispersed diamonds prepared according to any one of examples 17, 18, 19. (We took 40 wt.% Powder of refined nanodispersed diamonds and 60 wt.% Powder with graphite (carbon) on the surface, example 17, or 50 wt.% to 50 wt.%, example 18). Stirred in the mixer for 2-3 hours. Static synthesis diamond powder with a particle size of 40-60 μm in the amount of 25 vol.% Of the total billet volume was added to the batch based on nanodispersed diamonds. The mixture was mixed according to examples 17, 18, 19, pressed blanks. The preforms were placed in a high-pressure apparatus; they were sintered at a pressure of 4.0 GPa and a temperature of 1200 ^° C for 30 s.

 The sintered billet was a polycrystalline cake in which large diamond grains are connected by a nanocrystalline bond based on nanodispersed diamonds. At the same time, we obtained blanks with quality parameters the same as in example 19.

 Example 21

 The mixture was prepared and sintered according to Example 20. As a filler, a mixture of powders of diamond and cubic boron nitride in any ratio (from 1 to 100 wt.%) Between them was used. As a result, a material was obtained consisting of filler particles and a nanocrystalline binder bonding them with quality parameters the same as in Example 18.

 Example 22

 The preparation and sintering of the mixture was carried out according to example 20 or 21. As large diamond particles, diamond particles obtained in examples 1-11 with enlarged (see Fig. 17) diamond particle sizes (from 1 to 500 μm) were used. As a result, a billet was obtained with material quality parameters the same as in Example 18.

 Example 23

The mixture was prepared, the initial blanks were pressed according to examples 16-22. A silicon layer was placed over the preform. The treatment was carried out at a temperature of 1400-1600 ^o C, the pressure and processing time was set according to examples 16-22.

 The result was a diamond billet impregnated with silicon, which had a higher quality in the absence of porosity (see Fig.11).

 Example 24

 The mixture was prepared according to examples 23 or 16-22. Large particles of diamond or cubic boron nitride, or a mixture thereof (as in examples 20-23) were added to the charge. Then the mixture was stirred and pressed blanks. A silicon layer was placed over the preform. After sintering, a composite superhard material was obtained consisting of a nanocrystalline binder impregnated with silicon and large powders of superhard materials bound by this binder.

 The resulting material has a higher quality due to the lack of porosity and the formation of silicon carbide (SiC) along the grain boundaries (see Fig. 11).

 Example 25

 We took powder of nanodispersed diamonds without graphite (carbon) on the surface or coated with carbon. Conducted graphitization of the surface of the powder particles (according to any one of examples 2, 3, 6). As a result, a material was obtained on the basis of nanodispersed diamonds coated with graphite, the particle sizes of which are made nanometric and made in the form of a powder.

 In the process of holding the material at atmospheric, low or high relative to atmospheric pressure, the material is able to spontaneously coagulate. As a result, larger diamond particles are formed compared to the initial nanodispersed diamonds. The shape of the particles can be spherical (see Fig. 12), in the form of fibers (see Fig. 13), flakes (see Fig. 14), or round (see Fig. 15).

 The material can be used traditionally as an anti-friction additive, as an additive in composite materials based on metals, polymers.

 The same material can be used as a component of the mixture to produce new materials: for the manufacture of diamond billets and composite superhard materials, to obtain larger diamond particles compared to particles in the starting material, as well as for the synthesis of diamond particles by traditional methods.

 Example 26

 The powder was taken according to example 17. At least 1 wt.% Powder of refined nanodispersed diamonds was added to it, mixed for 2-3 hours in a mixer. Received the material in the form of a powder. The areas of use are the same as in Example 25. The difference between this material is that, along with the particles described in Example 25, particles with faceting are formed (see Fig. 16). This also increases the number and size of the resulting particles in comparison with the material of example 28.

 The material of examples 25 and 26 can be used to reduce the synthesis time and increase the yield of diamond particles using traditional methods.

 Example 27

 A powder of a material based on nanodispersed diamonds was taken (according to Example 25 or 26), mixed with a metal catalyst (any standard catalyst: Mn, Ni, Fe) in a ratio of 50 wt.% To 50 wt.%.

 The mixture was subjected to high pressure and temperature treatment using standard technology [2]. As a result of using this mixture, the processing time of the mixture was reduced to obtain the same result as in the above source, and a greater yield was obtained.

 Example 28

 Used any method for producing diamond particles by a method with increased particle sizes from 1 to 500 microns (examples 1-11). The obtained powder was used in the manufacture of parts of a processing tool using traditional binders [3] using traditional binders, for example, a tool in the form of tablets on a copper-tin binder for processing optics. As a result, a diamond-based processing tool with corresponding characteristics was obtained.

 Example 29

 The preparation and sintering of the mixture were carried out according to examples 17, 18, 20, 21, 22, 23, 24, 25. Received blanks that can be used after machining as an insert for a cutting or forming tool (for processing ceramics, non-ferrous metal alloys, as die, or the ruling tool).

 Thus, the claimed invention in comparison with the known technical solutions allows to obtain the following technical results.

 1. The method allows to obtain particles from 1 to 500 microns with a single or polycrystalline structure. At the same time, the formation of fibers and flakes with a diamond structure can occur.

 2. Particles synthesized by the proposed method can be of several types: spherical, oval, with faceting, irregular shape.

 3. The amount of non-combustible impurities in the particles synthesized according to the invention is not more than 2 wt.%, Therefore, the diamond particles are colorless and, as a rule, transparent.

 When implementing the invention, a charge of the following composition is used: nanodispersed diamond with graphite (carbon) of nanometric size deposited on the surface of its particles with or without the addition of refined nanodispersed diamonds. The specified charge is a material with the ability to spontaneous diamond formation and enlargement of diamond particles in a wide range of pressures and temperatures, including under normal conditions.

 The use of the charge in accordance with the claimed method allows to obtain diamond particles in the specified range (1-500 microns), and also use it to increase the yield of diamonds in traditional technologies for producing synthetic diamond.

 The method of producing diamond particles allows to obtain diamonds with sizes greater than 500 microns with lower costs and at higher productivity than the known methods for producing synthetic diamonds of this size.

 The main advantages of the claimed invention upon receipt of polycrystals are as follows.

 1. No need to use binder catalysts that reduce the physical and mechanical properties of the resulting workpieces. The binder that is used in the present method in the manufacture of preforms is a powder of nanodispersed diamond coated with graphite and / or carbon, the particle sizes of which are made nanometric. At the same time, in the heat treatment process, non-diamond carbon is recrystallized into diamond or diamond-like carbon, which binds nanodispersed diamond particles, and sintering of the resulting workpiece occurs at relatively low pressures, temperatures, and in a short time.

 2. During the heat treatment, a material is formed that has a highly dispersed (crystal size 10-1000 nm) structure, a microhardness of at least 60 GPa and an amount of non-combustible impurities of not more than 2 wt.%, Which allows it to be used as cutting and / or forming inserts and to produce highly efficient processing of difficultly processed materials, including ceramics, non-ferrous metal alloys.

 The use of a mixture based on nanodispersed diamonds allows sintering of a material containing large powders of superhard materials at lower sintering conditions compared to traditional modes.

 4. A material based on nanodispersed diamonds acts as a binder in the form of a nanocrystalline binder for large powders of superhard materials, in particular diamond, and improves the properties of preforms obtained on the basis of these powders.

 5. The use of the inventive charge based on nanodispersed diamonds allows melt impregnation of silicon during sintering, which increases the characteristics of the materials obtained, including with the addition of coarse-grained powders of superhard materials.

 6. The ability to obtain diamond powders with specified particle sizes by crushing the resulting workpieces based on nanodispersed diamonds.

 In addition, the advantages of the claimed invention in comparison with the known technical solutions are as follows.

 1. The invention allows to abandon the use of high pressures and temperatures in the synthesis of superhard materials. In the general case, the driving force causing the transition of layered modifications to dense ones and the growth of particles of dense carbon modification (boron nitride) is the tendency of a system in a nonequilibrium dispersed state to minimize free energy. In this case, the charge can be subjected to relatively low pressures and temperatures to increase the yield and size of the synthesized particles and reduce the process time. At the same time, according to existing traditional concepts, the synthesis of superhard materials from "loose" modifications essentially requires high pressures, temperatures and catalyst metals, which dissolve the feedstock and reduce the synthesis parameters. According to the claimed invention, the starting material is used for the synthesis in a finely dispersed "active" state, therefore, there is no need to use metal catalysts, which, in principle, does not exclude their use.

 2. The invention allows, along with refined powders of nanodispersed diamonds, to use unrefined, which reduces the cost of the final product.

 3. There is no need to use complex technological equipment.

 4. There is no need for chemical cleaning of powders obtained by the proposed method.

 5. Low energy consumption.

 6. Ecological cleanliness.

SOURCES OF INFORMATION TAKEN INTO ACCOUNT AT EXAMINATION
1. Kurdyumov A.V. et al. Structural Features of Nanodispersed Diamonds of Dynamic Synthesis, Journal of Superhard Materials, 4 (114), 1998, Kiev, HAH of Ukraine, Institute of Superhard Materials, pp. 23-29.

 2. Fedoseev D.V. et al. Crystallization of diamond. M .: Nauka, 1984.

 3. Synthetic superhard materials: In 3 tons. Synthesis of superhard materials. Redkol. : Novikov N.V. (ed.) and others. - Kiev: Naukova Dumka, 1986.

 4. Danilenko VV Dynamic synthesis of diamond. Report at the seminar on new materials and their application in mechanical engineering. United Nations. Economic Commission for Europe. Kiev (Ukraine), October 13-16, 1992

5. RF patent 2050319, IPC ⁶ C 01 B 31/06, publ. 12/20/95, bull. 35.

 6. Synthesis of heat-resistant polycrystals of diamond. Mazurenko A.M., Rakitsky E.V., Rakitskaya L.I. Collection of scientific. doc. "Technique and technology of high pressure." - Minsk: Urajay, 1990, p. 188-188.

7. RF patent 2137242. IPC ⁶ H 01 J, 1/14, 1/30, 09/10/1999 (prototype).

8. SU 1655080, IPC ⁶ C 01 B 31/06, 10.09, 1995 (prototype).

9. Patent application in the Republic of Belarus for invention 970528, IPC ⁶ B 23 F 3/00, C 01 B 31/06, publ. 12/30/98, bull. 4.

10. RF patent 2131805, IPC ⁶ B 24 D 3/16, publ. 06/20/99, bull. 17 (prototype).

Claims (10)

1. A method of producing diamond particles, mainly for the manufacture of diamond-containing material, in which particles of nanodispersed diamonds are subjected to predetermined pressures and temperatures, characterized in that particles of graphite or carbon of nanometric sizes are applied to the surface of diamond particles. 2. The method according to claim 1, characterized in that the particles of graphite are applied to the surface of the diamond particles by heat treatment of the purified powder of nanodispersed diamonds, with the graphitization of their surface layer, heating them in vacuum at a temperature of from 1000 to 1500 ° C. 3. The method according to claim 1, characterized in that graphite is applied to the surface of diamond particles by heat treatment of a crude powder of nanodispersed diamonds with graphitization of carbon located on the surface of diamond particles by heating in an inert gas or vacuum at a temperature of from 1200 to 1500 ° C. 4. The method according to claim 2 or 3, characterized in that the graphite layer is increased by additionally depositing carbon on the surface of the obtained particles from carbon-containing gas by cooling these particles to a temperature below 300 ° C and feeding carbon-containing gas heated to a temperature into the reaction volume from 300 to 1000 ° C. 5. The method according to claim 1, characterized in that the surface of the initial diamond particles is moistened with a carbon-containing liquid or carbon-containing groups of carbon-containing gas are deposited on the surface of these particles, heating the gas to a temperature of 300 to 1000 ° C and maintaining the temperature of the diamond particles not more than 300 ° FROM. 6. The method according to claim 1, characterized in that the particles of refined nanodispersed diamonds are mixed with particles of graphite of nanometric sizes, and the processing of the resulting mixture is carried out at a pressure of from 0.133 × 10 ^-10 to 2.0 GPa and a temperature of from 20 to 1200 ° C shutter speed from 30 s to 6 hours 7. The method according to claim 6, characterized in that particles of graphite or graphite-like boron nitride with a size of not more than 1 μm in an amount of from 10 to 50 wt.% Or amorphous boron with a particle size of not more than 1 μm in an amount of up to 10 are added to the charge wt.%, as well as a carbon-containing liquid in an amount of from 10 to 100 vol.% of the volume of the obtained mixture. 8. A method for producing diamond crystals, in which diamond particles are treated by pressure and temperature in a carbon-containing medium, characterized in that nanodispersed diamonds are used as diamond particles, while graphite or carbon, the particle sizes of which are nanometric, are applied to the surface of these particles. , and after receiving the final product, the latter is classified by separating diamond crystals. 9. A method of producing preforms containing diamond particles, in which preforms are formed from a charge, the preforms are placed in a container and sintered at elevated pressure when heated, characterized in that nanodispersed diamond powder with crystallite sizes from 2 to 10 nm is used as a charge; powder of nanodispersed diamonds, on the surface of the particles of which graphite or carbon is deposited, the resulting mixture is sintered at a pressure of 2.5 to 4.0 GPa and a temperature of 800 to 1200 ° C with a holding time of 10 to 60 s, with a ratio of components, wt. %: Nanodispersed diamond powder with crystallite sizes from 2 to 10 nm 10 - 50 Nanodispersed diamond powder with graphite or carbon deposited on its surface 10. The method according to claim 10, characterized in that an additional layer of silicon is placed above the preform, and the treatment is carried out at a temperature of from 1400 to 1600 ° C.

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