RU2636536C1 - Method of manufacturing carbon-graphite products - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: preparation of a mixture based on carbon-containing filler is carried out, mixture in form of layer is placed in the area of product moulding, and its radiation treatment is conducted with laser radiation in inert gas atmosphere. Preparation of mixture is carried out by introducing a binder into the carbon-containing filler, and the obtained mixture is placed in the area of product moulding in form of successively applied layers of 0.15-0.5 mm, each of which is irradiated with laser radiation heated to the temperature of 1000°C to 1800°C with constant blown inert gas. Before overlaying next layer, the previous layer is cooled to 90-100°C, and either a high molecular organic binder or aromatic resins are used as a binder. In particular embodiments of the invention, coke or graphite powder in fraction of 20 to 150 mcm is used as the carbon-containing filler. High molecular organic binder, or C8-C10 aromatic resins, or combined C7-C11 resins are used as a binder. Layers of mixture are irradiated with laser radiation with wavelength of 1070 nm, radiation power of 340 W, with beam speed of 4-5 mm/s, and beam diameter of 6-7 mm. Laser source is solid-state laser, or Ti:Sa laser, or Yb:YAG laser, or Nd:YVO laser, or Nd:YLF laser, or Nd:YAG laser with wavelength of 0.5-3 mcm, power of 50-500 W with uniform radiation density in the beam.EFFECT: improving the quality of products made of graphite, carbon-carbon and silicon carbide composites, and obtaining products with high density, uniformity and increased crack resistance, reducing the time of manufacturing products and providing variability in the manufacture of products with different characteristics.5 cl, 2 dwg, 3 ex

Description

The invention relates to the production technology of products from graphite and carbon-carbon and silicon carbide composites. The basis of the invention is the task of manufacturing fine-grained graphite, carbon-carbide-silicon, carbon-metal composites using pyrolysis of special mixtures with high-intensity laser radiation. It can also be used for the manufacture of fine-grained graphite, carbon-silicon carbide, carbon-metal composites by means of pyrolysis of special mixtures with high-intensity laser radiation.

A known method of carbonization and activation of carbon material in a rotary kiln with external heating, with an inlet and discharge side, with a downward inclination towards the discharge side, annular partitions with intervals along the furnace to control the movement of material and lifting bars between partitions for mixing the material, parts lifting the material up and causing the raised material to cascade into the lower part of the rotating body; comprising: supplying material to the loading end of the furnace; the feed to the furnace is carried out in an atmosphere of water vapor or carbon dioxide substantially free of oxygen; maintaining the first zone of the furnace at a temperature sufficient to dry or remove solvent from the material without carbonization; maintaining the second zone of the furnace downstream of the first zone at a temperature sufficient to carbonize the material; maintaining the third zone of the furnace downstream of the second zone at a temperature sufficient to activate the carbonized material; and collecting material from the discharge side of the furnace [RU 2478573, C2, C01B 31/08, C10B 47/30, C10B 53/07, P27B 7/16, 04/10/2013]

The disadvantage of this method is the complexity of the technical implementation and, in addition, it is characterized by a relatively narrow scope, since it is not used to obtain finished products.

In addition, a method is known [RU 2520455, C2, C10B 55/00, C10C 3/04, 06/27/2014], comprising carbonizing the starting pitch, which is heat treated before carbonization in the presence of a condensing additive and air, while the heat treatment is carried out in the reactor by heating the initial pitch to a temperature of 300-400 ° C, carbonization is carried out by gradually heating the pitch to a temperature of not more than 750 ° C with a rarefaction in the reactor of 5-10 mm aq. Art., and the gases emitted during carbonization are captured and neutralized by mixing them with mineral acid or its vapors.

The disadvantage of this method is the relatively narrow scope, since the method can be used to obtain isotropic pitch semi-coke from the original pitch with a softening temperature of up to 100 ° C.

The closest in technical essence to the proposed is the method [RU 2591826, C2, C23C 26/00, C23C 8/46, B82Y 30/00, 07/20/2016], which consists in the fact that nanosized graphite powder is ground in an activator for 40 -45 minutes, then heptane is added to it, the mixture is ground for 10-15 minutes, then a suspension of heptane-graphite is applied to the steel surface with a thickness of 10 ± 1 μm and dried, and surface treatment is carried out by laser radiation with a pulse generation frequency of 20-100 kHz, with a power of 10-50 W and a scanning speed of 800-900 mm / s.

A feature of the method is that, to prepare the nanoscale powder, graphite of the GK-1 brand, or of the GE brand, or of the HORG brand, or activated carbon is used, and surface treatment with laser radiation is carried out in an inert gas atmosphere or in vacuum.

The disadvantage of the closest technical is the relatively low quality of the resulting carbon product, in particular, coatings for steel.

The problem that is solved in the proposed invention is to improve the quality of products from graphite and carbon-carbon and silicon carbide composites.

The required technical result is to improve the quality of products from graphite and carbon-carbon and silicon carbide composites, reducing the time for manufacturing products and ensuring variability in the manufacture of products with different characteristics.

The problem is solved, and the required technical result is achieved by the fact that, in the method according to which the mixture is prepared on the basis of a carbon-containing filler, the mixture is placed in the form of a layer in the molding area of the product and irradiated with laser radiation in an inert gas atmosphere, according to the invention, for preparing a binder is introduced into the carbon-containing filler and the resulting mixture is placed in the product molding area in the form of successively applied layers of 0.15-0.5 mm thick, each of which is coated laser radiation with heating to a temperature of from 1000 ° C to 1800 ° C with constant inert gas blowing, while before applying the next layer the previous layer is cooled to 90-100 ° C, and either a high molecular weight organic binder or aromatic resins are used as a binder .

In addition, the desired technical result is achieved by the fact that, as a carbon-containing filler, either coke or graphite powder is used with a fraction of 20 to 150 microns.

In addition, the desired technical result is achieved in that, as a binder, either high molecular weight organic substances, or aromatic resins C8-C10, or combined resins C7-C11 are used.

In addition, the required technical result is achieved by the fact that the mixture layers are irradiated with laser radiation with a wavelength of 1070 nm, the radiation power is 340 W, with a beam velocity of 4-5 mm / s and a beam diameter of 6-7 mm.

In addition, the desired technical result is achieved by the fact that, as a source of laser radiation, a solid-state laser or Ti: Sa, or Yb: YAG, or Nd: YVO, or Nd: YLF, or Nd: YAG with a wavelength of 0.5- 3 microns, with a power of 50-500 W with a uniform radiation density in the beam.

In addition, laser radiation is focused and scanned by the mixture layer using an automated control system, varying the laser beam diameter and heat treatment time depending on the parameters of the mixture and the required heating temperature,

The drawing shows:

in FIG. 1 is a diagram illustrating an example implementation of the method;

in FIG. 2 is a diagram of a laser carbonization process.

The proposed method for the manufacture of carbon products is implemented as follows.

As a filler, powder or coke or graphite is used with a fraction of 20 to 150 microns. As a binder, organic liquids with a high carbon content are used. For the production of dense graphites (density 1.5 g / cm3 and higher) by the proposed method, it is necessary to use binders that do not contain oxygen and nitrogen atoms, for example, either aromatic resins C8-C10, or combined C7-C11 resins. The use of binders containing oxygen atoms leads to the appearance and growth of pores during the pyrolysis of mixtures, and, as a consequence of this, weight loss. This is due to a chemical reaction with the formation of CO, CO2 and low molecular weight organic compounds.

The proposed method allows the use of organic substances with a high oxygen content for the manufacture of porous products or preforms with a lower density (0.3-1.2 g / cm3).

Due to the fact that the proposed method is based on an extremely high heating rate (more than 1000 ° C / s), and the heating is carried out by laser radiation, a limitation is placed on the thickness of the carbonized layer per scan. The optimal layer thickness is 0.15-0.5 mm. With a smaller thickness, the productivity of the method decreases, and it has been experimentally proved that with an increase in the thickness of the processed layer over 0.5 mm, the binder is partially carbonized: the binder located at a depth of more than 0.6 mm does not heat up to the required temperatures. In this case, an increase in the power density of the laser radiation leads to the evaporation of the filler from the surface.

In the manufacture of carbon-metal and carbon-carbide-silicon composites, fillers can be used powders of coke, graphite, silicon, inert with respect to carbon and a metal binder, as well as discrete ceramic or metal microfibers. The proportions of carbon / metal or carbon / silicon depend on the required quality characteristics of the resulting product and may vary. As binders, similar binders can be used as for the production of graphite products, or otherwise.

Heat treatment of mixtures for the manufacture of carbon-metal and carbon-carbide-silicon is carried out at a heating temperature from 1000 ° C to 1800 ° C. In this case, several acts of scanning by laser radiation are possible to reduce the temperature gradient in the heat-treated mixture. A lower heating temperature does not allow to provide the required quality of heat treatment, and a higher one leads to unjustified energy consumption.

An example of a specific implementation No. 1.

Coal coke, fractions of 40-140 microns, was mixed with ED-20 epoxy resin (GOST 10587-84) in mixing equipment in the proportion of 62% filler and 38% binder by weight. An even layer of the mixture with a thickness of 0.5 mm was applied to the product forming zone, for example, on a metal substrate, using specially prepared laboratory equipment. The heat-treatable mixture was placed in a laser system. Scanning by laser radiation (wavelength 1070 nm, radiation power 340 W) was carried out with a low beam velocity of 4 mm / s. The beam diameter was 7 mm.

To exclude combustion, the carbonization process was carried out in an argon atmosphere. When heated, the formation of gaseous pyrolysis products was observed. Next, the carbonized layer was cooled to a temperature of 90-100 ° C by blowing with an inert gas and heat removal from the substrate. Using special laboratory equipment, a layer of a heat-treated mixture with a thickness of 0.5 mm was applied to the carbonized layer. Then the process of pyrolysis and cooling was repeated. The number of completed iterations is 5. The obtained sample did not exhibit pronounced adhesion to the metal substrate. The density of the sample was 1.13 g / cm3.

An example of a specific implementation No. 2.

Coal coke, fractions of 40-140 microns, was mixed with liquid pyrolysis products (TU 2451-178-72042240-2006) in mixing equipment in a proportion of 67% filler and 33% binder by weight. Using a specially prepared laboratory equipment, an even layer of the mixture with a thickness of 0.5 mm was applied to the metal surface. The heat-treatable mixture was placed in a laser system. Scanning by laser radiation (wavelength 1070 nm, radiation power 380 W) was carried out with a low beam velocity of 5 mm / s. The beam diameter was 6 mm. To exclude combustion, the carbonization process was carried out with argon blowing. When heated, the process of formation of gaseous pyrolysis products was observed, but it was estimated to be less than when using ED-20. Further, the carbonized layer was cooled to temperatures of 90-100 ° C by blowing inert gas and heat removal from the substrate. Using special laboratory equipment, a layer of a heat-treated mixture with a thickness of 0.5 mm was applied to the carbonized layer. Then the process of pyrolysis and cooling was repeated. The number of iterations completed is 6.

The obtained sample did not exhibit pronounced adhesion to the metal substrate. The density of the sample was 1.58 g / cm3.

An example of a specific implementation No. 3.

Coal coke, fractions 40-140 microns and silicon powder fractions 80-120 microns were mixed with liquid pyrolysis products (TU 2451-178-72042240-2006) in mixing equipment in the proportion of 40% carbon filler, 25% silicon filler and 35% binder mass. Using a specially prepared laboratory equipment, an even layer of the mixture 0.5 mm thick was applied to the metal substrate. The heat-treatable mixture was placed in a laser system. 2 acts of scanning by laser radiation of the surface were carried out (wavelength 1070 nm, radiation power 340 W). The speed of the first scan is 6 mm / s, with a beam diameter of 7 mm. The second scan speed is 5 mm / s, with a beam diameter of 7 mm. The delay between scan events was 40 seconds. To exclude combustion, the carbonization process was carried out with argon blowing. When heated, the formation of gaseous pyrolysis products was observed.

When heated during the first act of scanning, the formation of gaseous pyrolysis products was observed. When heated during the second act of scanning, the formation of gaseous pyrolysis products was practically not observed. Further, the carbonized layer was cooled to temperatures of 90-100 ° C by blowing inert gas and heat removal from the substrate.

Using special laboratory equipment, a layer of a heat-treated mixture with a thickness of 0.5 mm was applied to the carbonized layer. Then the process of pyrolysis and cooling was repeated. The number of completed iterations is 5. The density of the sample was 2.27 g / cm3.

The analysis of microphotographs showed that the obtained samples demonstrate the uniformity of the microstructure: no stratification of the samples is observed, filler particles and pores are distributed homogeneously in the binder matrix and do not have a preferential orientation. Observation data allow us to expect a high degree of isotropy of the final products.

The carbonization process (Fig. 2) can be represented in the form of the following sequential transformations:

- the destruction of organic molecules, accompanied by the breaking of carbon-carbon and carbon-hydrogen bonds;

- the formation of molecules with condensed (multiple) carbon-carbon bonds;

- the formation of amorphous carbon precursors - polyaromatic compounds and carbon clusters;

- the formation of e graphite-like nuclei;

- growth of graphite nuclei;

- condensation of the nuclei in the core of amorphous carbon (sintering);

- evolution of gaseous degradation products (hydrogen, methane and other hydrocarbons).

Compared with known methods of carbonization, the proposed has the following advantages:

- reducing the porosity of the resulting amorphous carbon and increasing the ceramic yield due to the rapid heating of the layers of the mixture, which prevents the slow kinetic processes, such as the removal of low-boiling components of the mixture from the heating zone;

- increasing the crack resistance of the product, since the heat treatment of the mixture is carried out in layers and this reduces the temperature gradient between the surface and the internal structure of the product;

- the local nature of heating and inert gas blowing reduces the requirements for temperature resistance of the equipment, and the total temperature of the product does not exceed 300 ° C.

Thus, the proposed method improves the quality of products from graphite and carbon-carbon and silicon carbide composites and improves products with high density, uniformity and increased crack resistance. The application of the method allows to reduce the manufacturing time of products and to provide variability in the manufacture of products with various characteristics.

Claims (5)

1. A method of manufacturing carbon-graphite products, comprising preparing a mixture based on a carbon-containing filler, placing the mixture as a layer in the region of the molding of the product and irradiating it with laser radiation in an inert gas atmosphere, characterized in that the mixture is prepared by introducing a binder into the carbon-containing filler and placing the resulting the mixture in the field of molding the product in the form of successively applied layers with a thickness of 0.15-0.5 mm, each of which is irradiated with laser radiation with heating to t temperatures from 1000 ° C to 1800 ° C with constant inert gas blowing, while before applying the next layer the previous layer is cooled to 90-100 ° C, and a high molecular weight organic binder or aromatic resins are used as a binder. 2. The method according to p. 1, characterized in that as a carbon-containing filler using coke or graphite powder with a fraction of from 20 to 150 microns. 3. The method according to p. 1, characterized in that as a binder use a high molecular weight organic binder, or aromatic resins C8-C10, or combined resins C7-C11. 4. The method according to p. 1, characterized in that the layers of the mixture are irradiated with laser radiation with a wavelength of 1070 nm, a radiation power of 340 W, with a beam velocity of 4-5 mm / s and a beam diameter of 6-7 mm. 5. The method according to p. 1, characterized in that the solid-state laser, or a Ti: Sa laser, or a Yb: YAG laser, or an Nd: YVO laser, or an Nd: YLF laser, or an Nd: YAG laser, are used as a laser source. with a wavelength of 0.5-3 microns, a power of 50-500 W with a uniform radiation density in the beam.

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