The method of deposition of pyrocarbon coatings for articles in a fluidized bed

 

The invention relates to the production of carbon ceramic products with pyrocarbon coatings in chemical engineering, nuclear and electronic industries. The task of the technical solution is to increase the uniformity and quality of pyrocarbon coatings on ceramic products. Products with a characteristic dimension d are mixed in a fluidized bed with spherical particles double factional composition in a volume ratio of the product : large particles : fine particles, equal 1,0:(0,2-0,3):(0,1-0,2), the size of the particles is chosen in the range 0,l-0,2 d and 0.01 to 0.05 d, respectively, the density of the spherical particles is chosen in the range of 1.5-4.0 density products, and the concentration of hydrocarbons in time reduce speed up to 40-70 10-30 vol.% upon expiration of 0.1-0.3where- the total time of the deposition process. The invention enables the deposition of coatings on articles of complex configuration for achieving the strong ties of the coating to the substrate. 5 Il.

The invention relates to the field of production of carbon-graphite ceramics and can be used in chemical, atomic and electronic engineering.

Carbon-graphite materials with peroxitine barriers to the diffusion of fission fragments in the fuel elements (cartridges) of nuclear reactors (see Chernikov A. C. Fuel and fuel HTGR. - Atomic energy, 1998, T. 65, vol.1, S. 32-38).

In addition, these materials can be protective barriers when storing waste high level waste (HLW). At this time the container for the disposal of HLW can be a hollow sphere, cylinder, disk, etc. Before placing HLW in such containers spent fuel stand for decay of short-lived isotopes, evaporated gaseous fission products and later in the form of oxides, carbides or other compounds fractionary to spherical particles with a diameter of 0.5 to 5.0 mm After this pre-processing HLW place, for example, spherical (cylindrical) container, tightly closed with a lid and is directed to the operation of the deposition of protective coatings.

A significant drawback of the mentioned methods is that in places of fastening products is not identical throughout the product heat treatment and are not deposited protective coating with the desired characteristics.

With regard to capsulerebel, such as HLW, the latter is a decisive disadvantage. This is primarily due to lower retaining radionuclides parameters in places of fastening products, as well as value is incurred undesirable cracks, chips, etc. during operation of the container.

To address these shortcomings, the authors of this technical solution was found that the coated product in a fluidized bed of particles should make chaotic motion to ensure uniform coverage. The fact that the products having very different from unity the ratio of the diameter to the height d/h (cylinders with d/h<1, the disk with d/h>1), do fluidized bed regular, not chaotic motion. For example, the cylinders are oriented heights in the direction of flow and thereby the lower part of the cylinder are covered with a thicker layer of pyrocarbon than the top.

The closest in technical essence to the problem at hand is the method of deposition of pyrocarbon coating density of 1.7-2.0 g/cm3when the pyrolysis temperature of 1200-1600oFrom acetylene-propylene-argon mixture containing the last 13,65-28,0% vol. propylene and 25,35-52,0% vol. acetylene, the content of which amounts to 39-80% vol. (see U.S. patent, M CL C 23 C 11/00, 4194027 from 18.03.80 taken by the authors for the prototype).

However, this method, as shown by the experiments conducted by the authors, it is not possible to obtain a uniform coating, for example, for cylinders with an aspect ratio of height to diameter Bo the x coatings on ceramic products.

According to the invention this task is solved in that in the pyrolysis zone in a fluidized bed serves a mixture of hydrocarbon and inert gas, and the product with the characteristic size d are mixed in a fluidized bed with spherical particles double factional composition in a volume ratio of the product : large particles : fine particles, equal 1,0: (0,2-0,3):(0,1-0,2), the size of the particles is chosen in the range of 0.1-0.2 d and 0.01 to 0.05 d, respectively, the density of the spherical particles is chosen in the range of 1.5-4.0 density products, and the concentration of hydrocarbons in time reduce speed to about 40-70.% to 10-30% vol. upon expiration of 0.1-0.3where- the total time of the deposition process at a constant total flow of the mixture.

It was established experimentally that the use of particles monofuctional composition does not allow transfer of the covered product in a condition that ensures the uniformity of the coating on the product. When this product was stationary and was located on gazoraspredeleniye apparatus of the fluidized bed, and the particles were hovering over its surface.

When using double factional composition of the particles at a volume ratio of the product : large particles : fine particles, equal 1,0: (0,2-0,3): (0,1-0,2), and the particle sizes large rakastan covered products, when they were surrounded (washed) the particles of the fine and coarse fractions. Increasing the volume content of the particles of the coarse and fine fractions compared to the specified limits is impractical because it leads to increased surface deposition and reduce the efficiency of the process of building up layers on the products.

The dimensions of the particles, providing a stable dynamical state of the product in the fluidized bed, were determined in the range of 0.1-0.2 d and 0.01 to 0.05 d for coarse and fine fractions, respectively.

The density of the particles is determined within the range of 1.5-4.0 density products. Smaller values of this density has led to the release of particles from outside the reaction space, and large - to segregation of particles, preventing the translation of items in the dynamic state, providing favorable conditions for the deposition of coatings with satisfactory characteristics.

Current graphite materials (PG, HMP and others) have a porosity in the range of 20-30% relative to theoretical density of single crystals of graphite. When the open porosity of these materials is from 5.0 to 10.0% of the total porosity of the material. Thus, carbon-graphite materials can not be n the view of the role of pyrocarbon coatings on graphite materials is crucial to create a reliable diffusion barrier against radionuclide.

In this way pyrocarbon coatings with desired density and characteristics of the structure precipitated with fixed values of hydrocarbon concentration and temperature selected from the above relations parameters.

The resulting coating is uniformly deposited on the surface without penetration of pyrocarbon in the pores of the substrate.

Under such conditions is implemented less strong, the substrate with the coating than in the case when the initial stage of deposition of pyrocarbon is in the pores of the substrate with the subsequent release of the surface.

The proposed method differs from the known speed decrease of the concentration of hydrocarbons as the deposition of pyrocarbon coatings is illustrated by the following examples and illustrated in figures 1-5: Fig.1 - slice the appearance of cylindrical and tubular products; Fig.2 (a, b) - microstructure of pyrocarbon on the products; Fig.3 (a, b) - seal graphite; Fig.4 - zone pyrocarbon seal; Fig.5 - the appearance of products of various configurations.

Example 1. On graphite cylindrical and tubular products with a diameter of 4-5 mm and a height of 20 mm (Fig.1) in an amount of 200 pcs. besieged pyrocarbon coating at a volume ratio of what letestu particles 3.5 g/cm3. It was steady pseudogene particles and wool products, washed by the particles of the fine and coarse fractions. Pyrolysis of propylene (C3H6) in a mixture with argon was carried out at a temperature of 1350oWith and concentration With3H6in a mixture of 20 vol.%. The process time was 30 minutes Received pyrocarbon coating density of 1.85-1.90 g/cm3with homogeneous structure. However, the coating was deposited only on the surface without penetrating into the pores of the graphite material (Fig.2).

Example 2. Conditions of fluidization of the product were similar to those of example 1. Pyrolysis of propylene was carried out at a temperature of 1350oWith the concentration of CCH6at the initial stage was 55% vol. within 3 min, and then decreased stepwise to 20% vol. and for 27 min at a constant temperature deposited coating.

Received pyrocarbon coating density of 1.85-1.90 g/cm3with homogeneous structure. The coating was deposited not only on the surface and in the pores of the material products (Fig.3).

Example 3. Conditions of fluidization products similar to example 1, and the conditions of deposition of pyrocarbon coatings - example 2 except for the duration of the first stage of pyrolysis (9 min) when the total is the further increase in the duration of this stage was not feasible due to significant accumulation of the particulate products of pyrolysis, hindering the process of deposition.

The advantages of the proposed method of deposition of pyrocarbon coating in a fluidized layer in comparison with the known are primarily in the possibility of obtaining coatings on articles of complex shape and with different sizes (Fig.5), as well as coatings, quite firmly connected to the substrate, which should indicate high performance products based on them.

Claims

The method of deposition of pyrocarbon coatings for articles in a fluidized bed, comprising a feed zone of the pyrolysis of a mixture of hydrocarbon and inert gas, characterized in that the product with the characteristic size d are mixed in a fluidized bed with spherical particles double factional composition in a volume ratio of the product: large particles: fine particles, equal 1,0:(0,2-0,3): (0,1-0,2), the size of the particles is chosen in the range of 0.1-0.2 d and 0.01 to 0.05 d, respectively, the density of the spherical particles is chosen in the range of 1.5-4.0 density products, as the concentration of hydrocarbon in time reduce speed up to 40-70 10-30 rpm. % after a 0.1 to 0.3where- the total time of the deposition process, when

 

Same patents:

The invention relates to the field of chemical deposition from the vapor phase and, in particular, to plazmostimulirovannom chemical deposition from parasol phase of high-quality diamond-like carbon films on partially restricted surfaces or surfaces with a high degree of uncouthness

The invention relates to the formation of a coating of amorphous carbon with a polymer tendency on the substrate of polymer material having the shape of the vessel that is to be obtained, such as a bottle or vial, using plasma excited by electromagnetic waves

The invention relates to high-temperature composite materials obtained by the infiltration of gas phase chemical substances and deposition of matrix binder material in the porous structure of the

The invention relates to the field of surface modification of materials and can be used to improve the service characteristics of the dielectric sheet and roll materials

The invention relates to the technology of carbon materials by deposition from the gas phase layers of pyrolytic carbon with a high degree of ordering of the crystal structure on the surface of various materials
The invention relates to the field of microelectronics and can be used to create carbon-containing coatings with a new and unique properties

FIELD: metal science; protection of materials against external and corrosive attacks.

SUBSTANCE: proposed method for producing diamond-like films designed for encapsulating solar photocells to protect them against chemical, radiation, and mechanical damage includes variation of ion kinetic energy, plasma discharge current, and spatial density distribution of plasma incorporating C+, H+, N+, and Ar+ ions by acting upon ion current from radial source with electric field built up by stop-down, neutralizing, and accelerating electrodes. Spatial plasma distribution is checked for uniformity by measuring plasma current density on solar photocell surface whose temperature is maintained not to exceed 80 oC. In the process substrate holder makes complex axial movement in three directions within vacuum chamber. Diamond-like films produced in the process on solar photocell surface area over 110 cm2 are noted for uniformity, difference in their optical parameters variable within desired range is not over 5%.

EFFECT: enhanced adhesive property, microhardness, and resistance of films to corrosive attacks.

5 cl, 12 dwg, 2 tbl

FIELD: the invention refers to application of covers in a liquefying layer particular to an arrangement for settling covers in a liquefying layer.

SUBSTANCE: the arrangement for settling covers in a liquefying layer has a chemical reactor of a cylindrical form and a system of feeding with liquefiable gas, the inner surface of the cylindrical reactor is provided with vertical grooves located on ribs of regular polygons inscribed into the inner diameter of the reactor. At that the number of grooves is chosen in the limits 3-20, the grooves in the section have a form of an equilateral triangle and for a reactor with a diameter of 20-100 mm the relation of squares of transversal sections of the reactor and of all grooves is in the limits 100-200.

EFFECT: the invention provides stability of a liquefying layer at essential increasing of the particles' mass in the process of applying a cover.

1 cl, 1 dwg

FIELD: processes of chemical infiltration or chemical deposition from vapor phase, case hardening in furnace.

SUBSTANCE: method is used for monitoring process realized in furnace with use of gas reagent containing at least one gaseous hydrocarbon. Method comprises steps of adjusting working parameters of furnace; adding into furnace gas-reagent containing at least one gaseous hydrocarbon; discharging from furnace exhaust gases that contain by-products of gas-reagent reaction; washing out exhaust gases by means of oil that absorbs resins present in exhaust gases; receiving information related to process according to measured quantity of resins absorbed by oil. It is possible to change working parameters of furnace such as temperature, pressure in furnace, gas-reagent consumption and composition.

EFFECT: possibility for monitoring process in furnace without special apparatus of infiltration furnace.

14 cl, 1 dwg, 1 ex

FIELD: carbon particles.

SUBSTANCE: invention relates to technology of preparing particles having monocrystalline diamond structure via growing from vapor phase under plasma conditions. Method comprises step ensuring functioning of plasma chamber containing chemically active gas and at least one carbon compound and formation of reactive plasma, which initiate appearance of seed particles in the plasma chamber. These particles ensure multidirectional growing of diamond-structured carbon thereon so that particles containing growing diamond are formed. Functioning of plasma chamber proceeds under imponderability conditions but can also proceed under gravitation conditions. In latter case, seed particles and/or diamond-containing particles in reactive plasma are supported under effect of external gravitation-compensating forces, in particular by thermophoretic and/or optic forces. Temperature of electrons in the plasma are lowered by effecting control within the range from 0.09 to 3 ev. Chamber incorporates plasma generator to generate plasma with reduced electron temperature and device for controlling forces to compensate gravitation and to allow particles to levitate in the plasma with reduced electron temperature. This device comprises at least one levitation electrode for thermophoretic levitation of particles in plasma with reduced electron temperature or an optical forceps device.

EFFECT: enabled efficient growing of high-purity duly shaped particles with monocrystalline diamond structure having sizes from 50 μm to cm range (for instance, 3 cm).

19 cl, 5 dwg

FIELD: metallurgy.

SUBSTANCE: invention refers to plastic package with inside surface of wall coated with diamond-like film; invention also refers to device for fabricating this package and to method of package fabricating. The device contains an electrode encompassing the package and forming one portion of a chamber for pressure fall where the package and a facing electrode located inside the package above an aperture are arranged. The said electrodes face each other and are divided with an insulating body forming portion of the pressure fall chamber. A device for source gas supply contains an inlet pipe of supplied gas. There are also a pumping out device and a device of high frequency supply. The method includes pumping out the package contents till achieving the pressure less or equal to specified, then introduction of source gas for generating plasma, termination of pumping out and decreasing the rate of introduction of the source gas to the value less than the rate of introduction at the moment of change, generating plasma for formation of diamond-like carbon film on the interior surface of the plastic package wall. Thus the package with film is produced; the said film has equal level of oxygen impenetrability; and colouring of film formed at the throat portion of the package is avoided.

EFFECT: production of package with diamond-like carbon film with uniform level of oxygen impenetrability.

25 cl, 24 dwg, 7 tbl

FIELD: technological processes.

SUBSTANCE: electrode that surrounds the receptacle and forms part of pressure reduction chamber intended for receptacle installation and electrode that is installed next to receptacle neck above its opening are installed one opposite to each other and separated with insulating body. This body forms part of pressure reduction chamber. Inlet tube of gas is made of insulating material for guiding gas that is supplied to the mentioned chamber with the help of supply facility of gas that is transformed into plasma for application of diamond-like film of coating onto receptacle wall internal surface. Tube is installed on facility for exhaust of gas that is available in pressure reduction chamber from the bottom part of receptacle part with opening. High-frequency supply facility is connected to electrode that surrounds receptacle, therefore, it is possible to freely ignite plasma and execute discharge.

EFFECT: stabilisation of plasma discharge and prevention of dust adhesion to electrode.

16 cl, 12 dwg, 2 ex, 2 tbl

FIELD: chemistry.

SUBSTANCE: invention relates to method for control and simulation of compaction of at least one porous substrate with pyrolitic carbon by chemical gas phase infiltration. According to the method, a lot of one or several substrates to be compacted is placed into furnace, the said substrate is heated, reaction gas containing at least one carbon-source hydrocarbon is supplied to the furnace, pressure, at which reaction gas is capable to diffuse into the heated substrate pores with formation of pyrolitic carbon residue, is established in the furnace, and waste gas is released from the furnace via exhaust pipe connected to the furnace outlet. In waste gas, content of at least one substance chosen from allene, propyne and benzene is determined. According to measured content, process is controlled by setting at least one of the following parameters: flow rate of reaction gas supplied to the furnace, flow rate of at least one component of gas supplied to the furnace, time of gas transit through the furnace, substrate temperature and pressure inside the furnace. At least one of parameters is set so as to provide for almost constant measured gas content. Compaction process can be either controlled in real time or simulated.

EFFECT: possibility of real-time control and simulation of process of compaction of at least one porous substrate with pyrolitic carbon using chemical gas phase infiltration.

12 cl, 8 dwg, 8 tbl, 10 ex

FIELD: chemistry.

SUBSTANCE: invention relates to microstructural technologies, namely to nanotechnology, in particular, to method of obtaining fibrous carbon nanomaterials which consist from carbon nano-tubes, by method of precipitation from gas phase. Reactor is filled with inert gas and its central part is heated. Then reaction mixture containing carbon source and ferrocene catalyst source is injected, which under impact of temperature turns into vapour. Vapour is kept in hot zone by ascending inert gas flow, source of padding for precipitation of catalyst nanoparticles and growth of carbon nano-tubes being introduced into reaction mixture. As padding source used are complexes of macrocyclic polyesters with salts of metals selected from line Ca, Ba, Sr, Y, Ce, which have temperature of decomposition lower than catalyst source, and serve as continuous source of padding.

EFFECT: synthesis of carbon nano-tubes is performed continuously, which results in increase of carbon nano-tubes output.

1 dwg, 3 ex

FIELD: chemistry.

SUBSTANCE: invention relates to devices for carbon nanotubes production. Device contains reaction furnace with unit for supplying and introducing of ethanol vapours, holder of padding with padding, which has catalytic surface, and heating element. Inside of reaction furnace placed is reaction chamber, which contains separable part, joint with drive of axial movement. Unit of ethanol vapours supply contains evaporating cell with ethanol, joint with ethanol vapours input. Heating element is placed inside reaction chamber in padding zone. Device is supplied with generator of particle flow, placed in reaction chamber, and made in form of at least one conductive net, connected to source of alternating or/and source of continued voltage. At least one conductive net is made of catalytic material. Reaction chamber is made of quartz ceramics. In evaporating cell heater and ethanol temperature measuring instrument are placed. Inlet of ethanol vapours is made of conductive material, and is connected to source of alternating or/and source of continued voltage. Inlet of ethanol vapours is made in form of two pipes, which are coaxially placed one in the other with ability to move relative each other.

EFFECT: increasing nanotubes quality and device reliability.

6 cl, 1 dwg

FIELD: metallurgy.

SUBSTANCE: interior electrode for forming shielding film is installed inside plastic container with port and it supplies gaseous medium inside plastic container; it also supplies high frequency power to external electrode located outside plastic container, thus generating plasma of discharge on interior surface of plastic container and creating shielding film on interior surface of plastic container. The interior electrode for forming shielding film consists of a gas supplying tube containing gas propagation path and designed for supply of gas medium and of an insulating element screwed into the end part of the tube so, that it is flushed in it; the insulating element is equipped with a gas outlet communicating with the gas propagation path.

EFFECT: development of electrode for efficient forming of shielding film.

12 cl, 9 dwg

Up!