Heat-resistant composite diamond sintered article and the method of its production

FIELD: chemical industry; mining industry; other industries; methods of production of the heat-resistant composite diamond sintered articles.

SUBSTANCE: the invention is pertaining to the heat-resistant composite diamond sintered articles used in the capacity of the cutting tools, the tool used for the high-precision machining and to the jewelry branch. The diamond composite sintered article contains in the capacity of the article the diamond crystal and the very small amount of the non-diamond carbon and has the hardness according to Vickers of 85 GPa or more. The article is produced by the method providing for inclusion of the synthetic diamond powder having the average size of the grains of 200 nanometers or less, in the tantalum or molybdenum capsule, both heating and application of the pressure at usage of the apparatus for the synthesis under the super-high pressure in the thermodynamically stable conditions including the temperature of 2100°С or more and the pressure of 7.7 GPa or more. The technical result of the invention is production of the articles having the electric conductivity, the high thermal stability and having the brilliance and the glaze.

EFFECT: the invention ensures production of the articles having the electric conductivity, the high thermal stability and having the brilliance and the glaze.

6 cl, 4 ex, 3 dwg

 

The technical FIELD TO WHICH the PRESENT INVENTION

The present invention relates to heat-resistant diamond composite sintered product and method of its production.

Prerequisites FOR the CREATION of the PRESENT INVENTION

Hitherto known method of obtaining a diamond sintered products by means of sintering additives, such as a carbonate, or metal, for example cobalt, when using a standard apparatus for synthesis at high pressure (see the following patent publications 1 and 2). Also known another method for synthesis of diamond sintered products of high hardness with excellent heat resistance, which provides for the performance of technological operations sintering under conditions of higher pressure/temperature conditions than under standard processing when using a carbonate of alkaline earth metal as a sintering additive instead of metal sintering additives (see the following non-patent publication 1). However, molten carbonate having a high viscosity, affect the amount of grain and accordingly these sintered products have a relatively large grain size, comprising at least about 5 microns.

There is also known a method of sintering that do not involve the introduction of add is to, which provides for the conclusion of the diamond powder in a metal capsule without sintering additives and application directly to the external capsule ultra high pressure, instantaneously generated by the explosion or impact capsule metal plate, moving at high speed, thanks to ultra-high pressure generated by the shock or similar, so that under the action of compression of the shock load to form a synthesized diamond powder. However, if this method is used diamond powder having a grain size average of 250-500 nm, which is synthesized by static compression, it cannot be obtained any sintered diamond products, with high hardness, due to graphitization in the part of the diamond powder.

As one measure to address this problem, a method of obtaining diamond containing ultrafine grain, using a process of shock-compression when using synthesized shock polycrystalline diamond grains (patent publication 3). In patent publication 3 describes the Example 4, in which the synthesized shock polycrystalline diamond grains having a grain size in the range of 100-500 nm, is sintered by using a process of shock-compression Yes the population, components 71,8 HPa, with reaction times, amounting to several tens of microseconds. This sintered product has a hardness, component 5000-6700 kg/mm2(49-65,7 GPA), and contains a small amount of graphite. That is, the hardness of the sintered product is low in comparison with the hardness component of approximately 100 HPa, natural single crystal.

The authors of the present invention has described a method of obtaining fine-grained diamond sintered products, which includes the introduction of the dihydrate of oxalic acid, which serves as a liquid phase CO2-H2O in carbonate to obtain a mixed powder, and application of natural diamond powder having a particle size variation (the range of the diameter distribution of the particles) from zero to 1 micron, the mixed powder for the formation of the layered structure (see the following patent publication 3 and non-patent publications 2 and 3). However, this method of obtaining essentially requires a high temperature component of the 2000°s or greater.

The authors of the present invention is also described a method similar to the above described method, which involves the sintering of fine-grained diamond powder having, for example, the particle size range from zero to 0.1 ám (see the following non-patent publication 4). In this case, any diamond with uchenogo products of high hardness cannot be obtained due to the presence of abnormal grain growth in the diamond.

Was recently published article, which describes a method of synthesizing diamond sintered product under pressure 12-25 HPa and at a temperature component 2000-2500°without sintering additives by reaction of direct conversion of graphite into diamond. In this article it is reported that the resulting diamond sintered product has the ability to transmit light (see the following non-patent publication 5).

Primary publication 1: Japanese patent publication No. 52-012126

Primary publication 2: Japanese patent publication No. 04-050270

Primary publication 3: Publication No. 02-030668 Japanese patent application laid

Primary publication 4: Publication No. 2002-187775 Japanese patent application laid

Non-patent publication 1: Diamond and related materials. Vol.5, PP 34-37, Elsevier Science S.A., 1996

Non-patent publication 2: Journal of the 41stHigh Pressure Symposium, p 108, the Japan Society of High Pressure Science and Technology, 2000

Non-patent publication 3: Proceedings of the 8thNIRIM International Symposium on Advanced Materials, pp 33-34, the National Institute for Research in Inorganic Materials, 2001

Non-patent publication 4: Journal of the 42ndHigh Pressure Symposium, p 89, the Japan Society of High Pressure Science and Technology, 2001

Non-patent publication 5: So Irifune and other "characterization of polycrystalline diamond synthesized by direct conversion of graphite using multisupport devices is a", 6thHigh Pressure Mineral Physics Seminar, 28 August, 2002, Verbania, Italy

A SUMMARY of the PRESENT INVENTION

There is the need to obtain a diamond sintered products, applicable as a tool with high performance in the field of cutting tools and tools for high-precision machining as an alternative to single crystals, previously highly restricted and valuable as jewelry. In particular, due to higher cutting speeds in oil drilling crowns for diamond drilling and special automotive components, it is desirable to obtain higher thermal stability of diamond tools, obtained by sintering.

To date diamond sintered product of high hardness with metallic or non-metallic sintering additive was obtained by sintering under high pressure/high temperature of 5.5 to 7.7 GPA. In this method of obtaining a diamond sintered products, involving the use of sintering additives, the material used as the sintered product, inevitably remains in the form of a solid body in the sintered product after sintering at high temperature/high pressure, which causes a decrease in the area of connection between the diamond grains. Compared to the ideal diamond sintered product, not terrasim of sintering additives, diamond sintered product with a sintering additive tends to have a lower hardness and lower properties due to chemical reaction between the diamond and sintering additive remaining in the sintered product. In addition, the standard synthetic method of obtaining sintered products does not imply the use of sintering additives, requires very high pressures and temperatures.

Natural diamond powder having a range of variation of particle size of 0 to 0.1 microns, can be sintered using sintering additives consisting of a liquid phase carbonate-C-O-N for a light synthesizing fine-grained diamond sintered product with high hardness and carbonate, homogeneous distributed between the diamond grains under high pressure of 7.7 GPA and a high temperature of 1700°or more (Japanese patent application No. 2002-030863, publication No. 2003-226578 posted requests).

To reduce the cost of synthesis of fine-grained diamond sintered products of high hardness when using carbonate as a sintering additive, the authors of the present invention attempted to synthesize diamond sintered product by coating diamond powder with hydrogen endings, having an average grain size of 100 nm, on a sintering additive consisting of a liquid phase carbonate-C-H, for the images is of a layered structure, and exposure of the layered structure sintering under high pressure/high temperature. As a result, although the extracted sample was layered cracks and partial infiltration of carbonate, homogeneous infiltration of the liquid phase carbonate-C-H as sintering additives could not be reached.

As a result of the study reasons for this, the authors of the present invention have come to the conclusion that synthetic diamond powder is prone to plastic deformation and the gaps between the diamond particles partially reduced due to the plastic deformation, preventing the seepage of molten sintering additives.

In addition, in the system that does not use a sintering additive, the authors of the present invention tried to sintering of natural diamond powder having a particle size range from zero to 0.2 μm, the pressure of 7.7 GPA and temperature of 2300°C for 15 minutes. The results showed that the diamond sintered product of high hardness is synthesized from natural diamond powder having a particle size range from zero to 0.1 ám.

The authors of the present invention found that the above problem is not unexpected occurs if the synthetic diamond powder with an average grain size of 200 nm or less is used as the source material is and is sintered under high pressure/high temperature equivalent to the conditions that are created in accordance with the standard method of obtaining a diamond sintered products, involving the use of sintering additives, such as carbonate. Based on this knowledge, the authors of this application has fully achieved the synthesis of heat-resistant and fine-grained diamond sintered products without the use of sintering additives.

In addition, the sintered product obtained by this method of obtaining, contains negligible amounts of non-diamond carbon in the quality of the product. That is, the sintered product formed as a composite sintered article of diamond crystal and non-diamond carbon, and it creates the conductivity. This Almazny carbon will be of graphitization in the part of the diamond powder used as the starting material. Thus, the resulting composite sintered article having electrical conductivity, can be subjected to the process of electric discharge machining. In addition, the composite sintered product has a Shine and gloss, which do not have standard diamond sintered product.

In particular, the present invention provides obtaining thermally stable diamond composite sintered product obtained by sintering of ultrafine synthetic is practical diamond powder, having the average grain size, average of 200 nm or less, without the use of sintering additives. Composite sintered product contains a diamond crystal and a small number of non-diamond carbon in the quality of the product and has a hardness according to Vickers, component 85 GPA or more.

The present invention also provides a method of obtaining the above-mentioned heat-resistant diamond composite sintered product, which provides for the conclusion of a synthetic diamond powder with an average grain size, average of 200 nm or less, in a capsule, derived from tantalum or molybdenum, the heat and pressure when the apparatus is used for synthesis at high pressure in a thermodynamically stable conditions, including temperature 2100°s or greater and a pressure of 7.7 GPA or more.

Compared to natural diamond powder in a state in which each of the diamond powder has approximately one grain size, synthetic diamond powder is subjected to plastic deformation. Compared to a powder having a wide particle size distribution, powder, with less wide particle size distribution, will be less wide particle size distribution between grains. Thus, if the source material used synthetic Alma is hydrated powder, having approximately uniform grain size and the least possible average grain size, heat-resistant diamond composite sintered product will be synthesized without any sintering additives through the use of plastic deformation, just taking place in the diamond grains, and a large surface energy characteristic of small diamond grains, as the driving force.

When using diamond powder having an average grain size of more than 200 nm, the surface energy of diamond grains will decrease with increasing grain size, which causes difficulties in the process of synthesizing diamond sintered product.

Heat-resistant diamond composite sintered product is synthesized using the method of obtaining corresponding to the present invention can be used not only for industrial purposes, for example in the tool with high performance in the areas of cutting tools and in oil drilling crowns for diamond drilling, require high heat resistance, but also for jewelry due to the advantage of a high refractive index characteristic of diamond, luster, specific for the diamond sintered products obtained without sintering additives, and the possibility of obtaining large sintered product.

SPO is about receiving, corresponding to the present invention can be implemented in terms of pressure/temperature equivalent to the standard method of obtaining a diamond sintered product in which the carbonate is used as sintering additives.

BRIEF DESCRIPTION of DRAWINGS

Figure 1 is a sectional view conceptually illustrating one example of capsule synthesis sintered product, which is filled with diamond powder, subjected to sintering by using the production method, corresponding to the present invention.

Figure 2 is a graph illustrating x-ray sintered product obtained in Example 1 variant implementation of the present invention ((a) before heat treatment, (b) after processing.

Figure 3 electron micrograph of the fracture surface of the sintered product obtained in Example 1 variant implementation of the present invention.

DETAILED DESCRIPTION of embodiments of the PRESENT INVENTION

In the method of obtaining a diamond sintered product corresponding to the present invention, as the source material used synthetic ultrafine diamond powder. Figure 1 is a cross section illustrating one example of capsule synthesis sintered product, which is filled with diamond powder, subjected to sintering by using a method of obtaining a match is it the present invention.

As illustrated in figure 1, the capsule 3, having a cylindrical shape obtained from tantalum, has a graphite disk 4A, attached to its bottom to prevent deformation of the capsule. Layer 2A of the diamond powder was formed on the graphite disk 4A through tantalum or molybdenum foil 1A under this pressure. Tantalum or molybdenum foil is used to separate layers of diamond powder from each other for the synthesis of sintered products having the desired thickness, separating the graphite disks from the layer of diamond powder, preventing the passage of the medium pressure in the capsule and sealing the liquid phase. Then on the layer 2A of the diamond powder is placed tantalum or molybdenum foil 1B. Similarly formed second, third and fourth layers 2B, 2C, 2D of the diamond powder with the help of intermediate tantalum or molybdenum foil walls 1C, 1D, placed between them. Then on the 2D layer of diamond powder was placed tantalum or molybdenum foil 1E, and tantalum or molybdenum foil 1E placed a graphite disk 4B to prevent deformation of the capsule.

This capsule was placed in an environment of pressure and created pressure to 7.7 GPA or more at room temperature, through the use of ultrahigh pressure apparatus, based on the static process is about compression, for example, apparatus for synthesis at high pressure belt type. Then, under this pressure, the capsule is heated to this temperature, component 2100°or more, to effect sintering. If the pressure is lower than the 7.7 GPA, the desired heat-resistant sintered product cannot be obtained even if the temperature is equal to or exceeds 2100°C. in Addition, if the temperature is less than 2100°C, the desired heat-resistant product can not be obtained even if the pressure is equal to or greater than the 7.7 GPA. It is necessary to limit the temperature and pressure to an absolute minimum, taking into account the possibility of the device, since the excessive temperature or pressure just leads to deterioration in the efficiency of energy use.

Synthetic diamond powder with an average grain size of 200 nm or less, obtained by grinding of synthetic diamond powder having a larger grain size, and classification of the crushed powder. In this work, the grain size is a measured value when using particle size analyzer type Microtrac UPA. This method of measurement is widely known (see, for example, publication No. 2002-35636 Japanese patent application laid). Such synthetic diamond powder is produced on an industrial basis (for example, under tor the new name MD200 (average grain size of 200 nm); MD100 (average grain size 100 nm), manufactured by Tomei Diamond Co., Ltd.).

EXAMPLE

(Example 1 of a variant of implementation of the present invention)

As the source material used is produced on an industrial synthetic diamond powder with an average grain size of 100 nm.

Received tantalum capsule cylindrical shape having a wall thickness, which is 0.8 mm and the outer diameter of 11.6 mm and a graphite disk, having a thickness of 2.6 mm, was attached to the bottom of the capsule to prevent deformation of the capsule. 250 mg of the diamond powder was placed on a graphite disk through the tantalum foil and pressed at the pressure of 100 MPa to form a layer of diamond powder. Then tantalum foil was placed on the layer of diamond powder and then a graphite disc, having a thickness of 2.6 mm were placed on this tantalum foil to prevent deformation of the capsule. The capsule was subjected to forging and then separated, the excess part of the upper graphite disk.

Then the capsule was placed in the medium pressure NaCl - 10% ZrO2and subjected to sintering under pressure of 7.7 GPA at a temperature of 2200°C for 30 minutes by using an apparatus for synthesis at high pressure belt type. After completion of the sintering capsule was removed.

Then the product, such as corbitant, formed on the surface of the sintered products were removed using a solution of hydrofluoric acid to nitric acid and each of the upper and lower surfaces of the sintered products were polished using diamond grinding wheel for flattening surfaces. The sintered product had a high resistance to polishing and the sintered product after grinding had an average value of Vickers hardness of 90 GPA or more.

This sintered product was subjected to heat treatment in vacuum at a temperature of 1200°C for 30 minutes to evaluate the heat resistance. After this treatment, the sintered product was kept similar hardness Vickers as before treatment. 2 shows the radiograph obtained sintered products. Figure 2(a) and figure 2(b) shows the x-ray before heat treatment in vacuum at a temperature of 1200°C for 30 minutes and radiograph after the heat treatment, respectively. As follows from the results given in figure 2(a), the diffraction line of non-diamond carbon is observed as a broad diffraction line of (002) graphite and found a diamond and a very small amount of non-diamond carbon (indicated in figure 2(a)point (•)). As follows from the results given in figure 2(b), this diffraction line is not changed by the position and intensively the tee. This shows that the number of non-diamond carbon after heat treatment has not changed. As shown in figure 3, by examining the microstructure of the surface fault, it was found that the sintered product contains fine grains having an average grain size of 80 nm.

(Comparative example 1)

Except that the sintering temperature was 2000°C, sintering was carried out similarly as in Example 1, variant implementation of the present invention. The obtained sintered product had poor resistance to grinding, and the average value of Vickers hardness was 50 HPa.

(Example 2 of a variant of implementation of the present invention)

Except that as starting material used is a synthetic diamond powder with an average grain size of 200 nm, and the sintering temperature was 2300°C, sintering was carried out as in Example 1, variant implementation of the present invention. The obtained sintered product had a significantly higher resistance to grinding and extremely high hardness. In particular, the average value of Vickers hardness was 85 GPA.

(Comparative example 2)

Except that as starting material used is a synthetic diamond powder with an average the size of grains of 300 nm, sintering was carried out in the same way as it was done in Example 2, a variant implementation of the present invention. In the obtained sintered product was observed layered cracks, and resistance to grinding was much lower than in Example 2, a variant implementation of the present invention. Thus, an excessively increased, the average grain size complicates the synthesis of diamond sintered products of high hardness.

INDUSTRIAL APPLICABILITY

Diamond sintered product corresponding to the present invention has excellent heat resistance, high resistance to polishing and high hardness. For example, this diamond sintered product is used in the finishing machining for materials that are difficult machining, for example aluminum alloys with high silicon content, or in the process of ultra-precision machining of metals or alloys, it can provide excellent performance when cutting and wire drawing. Among other things, this diamond sintered product has a sufficient heat resistance, suitable for high speed cutting in oil drilling crowns for diamond drilling and special automotive components. In addition, there is Almazny carbon, providing a composite specification is military products having electrical conductivity. These properties make possible the use of the technological process of electric discharge machining process of cutting the sintered product to reduce the cost of machining. In addition, the composite sintered product has a Shine and gloss, which do not have standard diamond sintered product. Sintered product can be given different configurations by means of laser machining, grinding and polishing, as well as by means of electric discharge machining. Thus, we can expect its use in jewelry as a black diamond with the brilliance and luster that cannot be obtained in the standard diamond sintered products.

1. Heat-resistant diamond composite sintered product obtained by sintering sverkhdolgosrochnogo synthetic diamond powder with an average grain size, average of 200 nm or less, due to the use of the apparatus for synthesis at high pressure by means of static compression process without the use of sintering additives, and the specified composite sintered product as the product contains diamond crystal and a small number of non-diamond carbon and has a hardness according to Vickers, component 85 GPA or more.

2. Pic is b obtain heat-resistant diamond composite sintered product according to claim 1, providing

conclusion synthetic diamond powder with an average grain size, average of 200 nm or less, in a capsule, derived from tantalum (TA) or molybdenum (Mo);

placing the capsule in the environment pressure; and

heating and application of pressure to the capsule in thermodynamically stable conditions, including a temperature of 2100°s or greater and a pressure of 7.7 GPA or more, by using the apparatus for synthesis at high pressure by means of static compression process.



 

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SUBSTANCE: the invention is pertaining to the production of the superfine-grained diamond sintered articles of the high purity and high hardness, which is intended for usage in the capacity of the wear-resistant material capable to let the light go through it, and may be used in production of jewels. The article has the size of the grain equal to 100 nanometers or less. For its manufacture the superfine-grained natural diamond powder having the granulometric spread of values from null up to 0.1 microns is subjected to desiliconization, to sublimation drying in the solution, inclusion into the tantalum or molybdenum capsule without the sintering additive, heating and application of the excessive pressure to the capsule using the device for the synthesis at the super-high pressure at the temperature of 1700°С or more and under pressure of 8.5 GPa or more, which meet the conditions of the thermodynamic stability of the diamond. The technical result of the invention is realization of the synthesis of the diamond sintered article at the more low pressure, than in the standard method and without usage of any sintering additive. The article has hardness according to Vickers - 80 GPa and more and is excellent concerning resistance to the tear and wear and the thermal resistance.

EFFECT: the invention ensures realization of the synthesis of the diamond sintered article at the more low pressure, than in the standard method, and without usage of any sintering additive, ensures its hardness of 80 GPa and more according to Vickers and the excellent properties concerning resistance to the tear and wear and the thermal resistance.

4 cl, 5 ex, 3 dwg

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SUBSTANCE: the invention is pertaining to the production of the superfine-grained diamond sintered articles of the high purity and high hardness, which is intended for usage in the capacity of the wear-resistant material capable to let the light go through it, and may be used in production of jewels. The article has the size of the grain equal to 100 nanometers or less. For its manufacture the superfine-grained natural diamond powder having the granulometric spread of values from null up to 0.1 microns is subjected to desiliconization, to sublimation drying in the solution, inclusion into the tantalum or molybdenum capsule without the sintering additive, heating and application of the excessive pressure to the capsule using the device for the synthesis at the super-high pressure at the temperature of 1700°С or more and under pressure of 8.5 GPa or more, which meet the conditions of the thermodynamic stability of the diamond. The technical result of the invention is realization of the synthesis of the diamond sintered article at the more low pressure, than in the standard method and without usage of any sintering additive. The article has hardness according to Vickers - 80 GPa and more and is excellent concerning resistance to the tear and wear and the thermal resistance.

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4 cl, 5 ex, 3 dwg

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2 cl, 2 ex

FIELD: electrochemical extraction of metals from complex compounds; purification of diamond synthesis products.

SUBSTANCE: proposed method includes electrochemical treatment of synthesis product in acid electrolyte for obtaining graphite-diamond product containing 0.5-2.0% of metallic admixtures and deposition of metallic nickel and manganese on cathode. During purification of diamond synthesis products at extraction of nickel and manganese in form of metallic product, electrochemical treatment is carried out in membrane-type electrolyzer at circulation of catholyte through second electrolyzer. Process is conducted in area of temperatures of 25-30°C at cathode current density in the first electrolyzer of 2-15 A/dm2 and 15-30 A/dm2 in the second electrolyzer; catholyte pH in the presence of 100-150 g/l of (NH4)2SO4 in it is maintained at outlet from the first electrolyzer of 5-7.5 and 2.5-5 at return.

EFFECT: possibility of performing nickel and manganese extraction and purification of diamond synthesis products in one cycle.

1 tbl, 6 ex

FIELD: treatment of diamonds.

SUBSTANCE: proposed method of change of diamond color includes the following stages: (i) forming reaction mass at presence of diamond in pressure-transmitting medium fully surrounds the diamond; (ii) subjecting the reaction mass to action of high temperature and pressure during required period of time; proposed diamond is brown diamond, type IIa; its color is changed from brown to colorless by subjecting the reaction mass to action of temperature of from 2200°C to 2600°C at pressure of 7.6 Gpa to 9 Gpa.

EFFECT: possibility of keeping diamond intact during treatment.

46 cl, 4 dwg, 1 ex

FIELD: treatment of diamonds.

SUBSTANCE: proposed method includes the following stages: (i) forming of reaction mass at presence of diamond in pressure-transmitting medium fully surrounding the diamond and (ii) action of reaction mass by high temperature and pressure during required period of time; diamond is of IIb type and its color is changed from gray to blue or dark blue or is enriched by action on reaction mass of temperature from 1800°C to 2600°C at pressure of from 6.7 GPa to 9 GPa (first version). Diamond of type II may be also proposed which contains boron and its color is changed to blue or dark blue by action on reaction mass by the same temperature and pressure (second version).

EFFECT: improved color of diamond by changing it from gray (brown-gray) to blue or dark blue.

31 cl, 4 dwg, 2 ex

FIELD: treatment of natural diamond for change of its color.

SUBSTANCE: proposed method includes the following stages: (i)forming of reaction mass at presence of diamond pressure-transmitting medium which fully surrounds it; (ii) action on reaction mass by high temperature and pressure during required period of time; proposed diamond is brown diamond, type IIa; its color is changed from brown to rose by action on reaction mass by temperature from 1900°C to 2300°C at pressure from 6.9 GPa to 8.5 GPa.

EFFECT: enhanced efficiency of enriching diamond color keeping its crystals intact.

30 cl, 4 dwg, 1 ex

FIELD: processes and equipment for working natural and artificial origin diamonds, possibly in jewelry for refining diamonds and for imparting to them new consumer's properties.

SUBSTANCE: method comprises steps of acting upon crystal with electron beam whose integral flux is in range 5 x 1015 - 5 x 1018 electron/cm2; annealing crystal in temperature range 300 - 1900°C and acting with electron beam in condition of electric field having intensity more than 10 V/cm at least upon one local zone of crystal for imparting desired color tone to said zone. Local action of electron beams is realized through protection mask. As irradiation acts in condition of electric field local flaws such as bubbles or micro-inclusions are effectively broken.

EFFECT: possibility for producing diamonds with different local three-dimensional colored images such as letters or patterns of different tints and color ranges.

2 dwg

FIELD: carbon materials.

SUBSTANCE: invention concerns manufacture of diamond films that can find use in biology, medicine, and electronics. Initial powder containing superdispersed diamonds with level of incombustible residue 3.4 wt %, e.g. diamond blend, is placed into quartz reactor and subjected to heat treatment at 600-900оС in inert of reductive gas medium for 30 min. When carbon-containing reductive gas medium is used, heat treatment is conducted until mass of powder rises not higher than by 30%. After heat treatment, acid treatment and elevated temperatures is applied. Heat treatment and acid treatment can be repeated several times in alternate mode. Treated powder is washed and dried. Level of incombustible impurities is thus reduced to 0.55-0.81 wt %.

EFFECT: reduced level of incombustible impurities.

4 cl, 3 ex

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