RU1791376C - Method for polycrystalline diamond material production - Google Patents

Abstract

Usage: as a superhard material in mechanical engineering, manufacturing, as well as a structural material in electronics and instrumentation. The essence of the method lies in the fact that before exposure to high pressure and temperature, an antifriction polyelectrolyte is introduced into the initial diamond powder as an organic additive until it is completely wetted in an amount of 10-40 wt.%, Mixed thoroughly, dried to remove excess water, and wiped through a sieve with the cell size is 2 mm, then the mixture is pressed at a pressure of 100-800 MPa, followed by annealing of the compacts at 250-500 ° C for 0.5-1 hours in air at a heating rate of 1 to 10 ° / min and further affect them high pressure and temperature in the field of diamond stability. 1 tab.;

Description

The invention relates to the field of production of diamond ceramics, which can be used as a superhard material in mechanical engineering, manufacturing, and also as a structural material in electronics and instrumentation

The aim of the invention is to increase the yield of material and the yield of suitable polycrystals.

This goal is achieved by the fact that before exposure to high pressure and temperature, an anti-friction polyelectrolyte is added to the initial diamond powder as an organic additive until it is completely wetted in the amount of May 10–40,%, thoroughly mixed, dried to remove excess water, wiped with | A sieve with a mesh size of 2 mm, then the mixture is pressed at a pressure of 100-800 MPa, followed by annealing of the compacts at 250-500 ° C for 0.5-1 hours in air at a heating rate of 1-10 ° / min and then act high pressure on them and the temperature in the diamond stability.

The antifriction polyelectrolyte forms an electrically charged layer on the surface of the diamond particles, which prevents direct contact between the particles due to electrostatic repulsion, and thereby reduces the internal friction in the powders, which provides a denser packing of the particles.

The use of a polymer electrolyte provides a higher surface charge density on diamond particles compared to monomers, which increases the antifriction properties of the additive.

The introduction of polyectrolite in an amount of less than 10 wt.% Does not provide completeness

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wetting the entire surface of the particles of dispersed diamond powders, which impedes the achievement of the goal. The presence of additives in quantities over May 40. % makes no sense because the surface of the particles is filled with a monolayer of the polyelectrolyte and the cessation of its further effect on the compressibility of the powder. As a result, the maximum attainable density of diamond compacts in the used range of low (up to 1 GPa) pressures is determined by the properties of a particular powder (dispersion, particle shape, and particle size distribution)

A pressure below 100 MPa is not enough to effectively compact the diamond powder. If the pressing pressure is above 800 MPa, the separation of the compacts is possible, as well as the likelihood of jamming and wear of the mold. The shape of the compacts corresponds to the useful volume of the pressure chamber.

To remove the antifriction polyelectrolyte after performing its functions, diamond annealing is carried out in air. To prevent destruction of the compacts due to intense gas evolution during decomposition of the organic additive, the heating rate should not exceed 10 ° / min. The lower limit of the annealing temperature (250 ° C) is determined by the decomposition temperature of the additive. Upper (500 ° C) - the possibility of the start of graphitization and oxidation of diamond. An annealing time of 0.5-1 hours is sufficient to evaporate the decomposition products of the additive from compacts with diameters up to 10 mm.

Annealed diamond blanks are subjected to a pressure of 6-8 GPa at a temperature of 1200-2200 ° C for 5-60 s.

The criterion for the shelf life of the obtained diamond crystals is the absence of cracks, distinguishable on the section with a magnification of 30x, as well as the distortion coefficient of

WE Kf (dmax - dmin) / dmax 100%, GD6 dmax AND

dmin is the maximum and minimum diameter of the sample, respectively, since all the samples are cylinders thinned in a central cross section.

EXAMPLE 1 20% vol. A 10% aqueous solution of triethanolammonium polyacrylate (PAKTEA), the mixture is thoroughly mixed until a homogeneous suspension is obtained and dried in air at 100 ° C for 5-10 minutes to prevent the mixture from flowing out between the walls of the mold. Compression of the resulting mass in a steel mold is carried out at a pressure of 600 MPa. Cylindrical compacts with a diameter of 4.5 mm and a height of 4.5 mm are placed in alundum boats in a muffle furnace, heated in air at a speed of 10 ° / min to 400 ° C and held there for 30 minutes. Annealed compacts weighing 0.17 g are placed in a tubular graphite heater with an inner diameter of 4.5 mm, an outer diameter of 7 mm and a height of 8.5 mm, are closed at the ends with graphite caps 2 mm thick and then placed in a container made of lithographic stone like toroid with a diameter holes 15 mm. A force is applied to the assembled chamber until a pressure of 8 GPa is reached, by passing an electric current it is heated at a speed of 100 ° / s, upon reaching a temperature of 1800 ° C, isothermal holding is carried out for 20 s, cooling at a speed of 100-200 ° / s and relieving pressure The resulting polycrystalline diamond sample has a maximum diameter of -4.1 mm at the ends, and a center diameter of 3.9 mm, a height of 4.0 mm, a density of 3.4 / cm3, and a shape distortion factor of 4.8%. The maximum radial shrinkage as a result of exposure to high P and T was 13%, and the yield of suitable polycrystals was 95%. The sintering yield was 0.17 g.

PRI me R 2. Take as the starting powder - detonation diamond brand DALAN DAG to 25 (25-100), consisting of particles of lamellar form 5-1 μm and a dispersed component of 500-50 nm, with a specific surface of 23 4 m / g, with a density of 3.4 g / cm3 and a bulk density of about 1 g / cm3. The amount of additive was 30 wt.%. Further, as in example 1, sintering at high pressure at T - 1600 ° C for 60 s. The yield of material compared to the prototype is 1.5 times higher (0.142 g compared to 0.123 g), the yield of suitable polycrystals is 95%.

Example 3. An ultrafine diamond (UDD) with an average particle size of 5 nm, a specific surface of 300 m / g, and a density of 3.15 g / cm3 was taken as the initial powder. The pressing pressure was 800 MPa, the annealing temperature of the compacts was 300 ° C. Further, as in Example 2. The yield of material is increased by 1.7 times, the yield of suitable polycrystals is 65%.

PRI me R 4. Pressings from diamond powder AFM 14/10, obtained, as in example 1, are heated in air at a speed of 1 ° / min to 250 ° C and incubated for 30 minutes. Further, everything is as in Example 1. The results averaged over 10 experiments do not differ from Example 1.

PRI me R 5. Pressings from powder AFM 14/10, obtained as in example 1, are heated in air at a speed of 10 ° / min to 500 ° C and incubated for 30 minutes Further, everything is as in example 1. The output for sintering averaged 1.165 g, the yield of suitable polycrystals is 90%, which is somewhat worse than in examples 1 and 4.

Example Pressings from detonation diamond of the Dalan brand, obtained as in Example 2, are heated in air at a speed of 10 ° / min to 350 ° C and held for 1 hour. Then everything is as in example 2. The results obtained on average also correspond to example 2.

Additional examples are given in the table.

The proposed method for producing polycrystalline diamond material allows one to increase the yield of the material by 1.3–1.7 times while increasing the yield of suitable polycrystals and most

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Claims (1)

more effective for compacting fine diamond powders obtained by dynamic methods. SUMMARY OF THE INVENTION A method for producing a polycrystalline diamond material, comprising introducing organic additives into the diamond powder, followed by high pressure and temperature in the field of diamond stability, characterized in that in order to increase the yield of the material and the yield of suitable polycrystals, polyelectrolyte is used as an organic additive 10% aqueous solution of triethanolammonium polyacrylate in an amount of 10-40% by weight of diamond powder, then the mixture is stirred until a homogeneous mass and p Precompression is carried out at pressures of 100–800 MPa, followed by heating at a rate of 1–10 ° in 1 min and annealing at 250–500 ° С for 0.5–1 h.)