RU2707596C2 - Method of producing titanium carbide nanopowder - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to inorganic chemistry and nanotechnology and can be used for production of wear-resistant abrasive materials, high-temperature ceramic materials and coatings, high-strength composite materials. Downward laminar flow of carrier gas 2 is fed into vertically oriented reactor 1 of heat-resistant dielectric material. From the inside of the reactor, titanium wire is introduced, heated in the high-frequency field of counter-current inductor 3 to the melting point, drop 4 of melted titanium is obtained at its end, a drop is suspended contactlessly between coils of the counterflow inductor and evaporation of metallic titanium from the drop surface. Carrier gas stream 2 continuously carries away titanium vapor from drop 4, provides condensation of the vapors into the titanium nanoparticles in condensation zone 5 and is directed to reaction zone 6, where carbon-containing gas-reagent 7 is also fed from leak 8. Obtained titanium carbide nanoparticles are transferred into cooling zone 9, trapped by filter and obtaining a commercial product in form of titanium carbide nanopowder in free-bulk condition with average particle size of less than 30 nm and with controlled ratio of titanium and carbon without halogens and oxygen. Titanium evaporation from drop 4 is filled by continuous supply of titanium wire. Carrier gas used is an inert gas, and the reagent gas is a hydrocarbon from a class of alkanes, alkenes or alkynes.

EFFECT: due to the process continuity, the technological cycle is simplified and the technological capabilities of the method are expanded.

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Description

The invention relates to the field of production of titanium carbide, in particular to the field of production of titanium carbide nanopowders by gas-phase methods.

The invention can be used to obtain wear-resistant abrasive materials, high-temperature ceramic materials and coatings, high-strength composite materials.

The prior art technical solutions for producing titanium carbide powder by gas-phase methods, including the preparation of precursors in the form of titanium particles with a pyrolytic carbon coating.

A known method of producing titanium carbide powder (Rasit Kos, Gregory C. Glatzmaier, Process for synthesizing titanium carbide, titanium nitride and titanium carbonitride, Patent US 5417952, C01B 21/076, C01B 31/34, C01C 3/08, 1995), in wherein the titanium powder, titanium dioxide or titanium salt is placed in a reactor, heated in an atmosphere of carbon-containing gas to a pyrolysis temperature and a porous coating of pyrolytic carbon is created on the particles, carbon-coated particles are heated in an argon atmosphere to a temperature of 1200-1600 ° C and maintained at a predetermined temperature until the titanium carbide production process is completed. Propylene is used as the carbon-containing gas, the pyrolysis temperature is selected from the range of 200-1000 ° C, and the required amount of carbon (34 wt.%) On the particles is achieved by repeating the pyrolysis cycles, while the coating quality is controlled by transmission electron microscopy, and the amount of pyrolytic carbon controlled by thermogravimetry.

In the known method, the particle size of the titanium carbide powder is determined by the particle size of the starting product. For example, the known method allows to obtain particles of titanium carbide with a size of 0.05-0.2 μm when using titanium dioxide powder with an average particle size of 0.03 μm as the starting product.

The known method has a complex technological cycle involving methods for controlling intermediate products. The known method does not allow to obtain a titanium carbide nanopowder in a continuous mode.

The prior art technical solutions for producing titanium carbide powder by gas-phase methods, including the chemical reaction of titanium halides with carbon-containing gases with the participation of reducing agents.

A known method for producing titanium carbide powder, in which a reaction gas mixture consisting of a titanium halide (e.g. chloride), reducing metal vapor (e.g. sodium or magnesium) and a hydrocarbon (e.g. methane) is heated in a cylindrical vertical stainless steel reactor to a temperature of 500-1250 ° C and provide a titanium reduction reaction and a reaction of reduced titanium with a hydrocarbon (Charles F. Davidson, Monte B. Shirts, Donna D. Harbuck, Production of titanium nitride, carbide, and carbonitride powders, Patent US 4812301, C01B 31/34, 1989). Argon is used as the carrier gas for the vapors of the reducing metal and titanium halide.

In the known method, the metal reducing agent is introduced in an amount of 110-150 weight. % of the amount required by stoichiometry to restore titanium halide, and the carbon-containing gas is introduced in an amount of 200-400 weight. % of the required stoichiometry for the formation of titanium carbide. The reaction product of the components of the gas mixture by a known method is a mixture of titanium carbide and metal halides of reducing agents. Metal halides are removed from the final product by washing with water, after which the final product is filtered and dried. The residual content of metal halides in the final product is 0.1 weight. %

The known method allows to obtain titanium carbide powder with a particle size of 0.1-0.5 microns. The known method does not allow to obtain a titanium carbide nanopowder without impurities of metal halides, and the purification stage significantly complicates the process cycle.

A known method of producing submicron titanium carbide powder in the reaction of titanium halide vapor, a carbon-containing gas and a reducing agent at a temperature of formation of titanium carbide (Larry R. Swaney, Preparation of submicron titanium carbide, Patent US 3812239, C01B 31/30, 1974). In the known method, titanium tetrachloride is mainly used as titanium halide, organochlorine compound is used as carbon-containing gas, and hydrogen, heated by a plasma torch or torch to a temperature of 1500-4000 ° C, is used mainly as a reducing agent. In the known method, the components are introduced into the reaction zone in amounts exceeding stoichiometric, in addition, a neutral gas (for example, argon) is additionally introduced into the reaction zone in order to control the size of the resulting particles and prevent their sedimentation. The known method allows to obtain submicron particles of titanium carbide with sizes of 0.02-0.35 microns. A significant disadvantage of this method is the formation of toxic reaction products containing halides (for example, hydrochloric acid).

The known method has a complex technological cycle, requires the use of plasma heating sources, which complicates the design of the equipment, and does not allow to obtain titanium carbide nanopowder without the formation of halides.

The prior art describes technical solutions for producing titanium carbide powder by gas-phase methods, including the chemical reaction of titanium metal or its compounds with carbon-containing reagents.

A known method for producing needle-shaped titanium carbide powder (Viktorov V.V., Kovalev I.N., Vavilov E.S., Zherebtsov D.A., Tolchev A.V., Musatov V.V., Method for producing titanium carbide powder , RF Patent No. 2627142 C1, СВВ 31/30, C01G 23/00, B22F 9/22, B82Y 30/00, 2017, Bull. No. 22), including the placement of titanium metal in the furnace, heating the furnace to 700 ÷ 850 ° C and supply for 90 ÷ 180 minutes to the titanium metal of the hydrocarbon component in gaseous form together with argon in the following ratio of components: hydrocarbon component 10 ÷ 50 vol. %, argon 50 ÷ 90 about. % As titanium metal, titanium powder, titanium shavings, a titanium sponge and various titanium-based alloys are used. Toluene and hexane are used as the hydrocarbon component.

The known method allows to grow on the surface of metallic titanium needle particles of titanium carbide with a diameter of 50-200 nm and a length of 0.5-7 microns. The powder obtained in a known manner contains unreacted titanium, which must be removed by treatment with hydrochloric acid solution, which contaminates the final product.

The known method has limited technological capabilities and a limited scope associated with the needle shape of the particles, and the need to remove unreacted titanium complicates the process cycle.

The known method does not allow to obtain a titanium carbide nanopowder in a loose bulk state without impurities.

The known method does not allow to obtain a titanium carbide nanopowder in a continuous mode.

A known method of producing titanium carbide powder in a fluidized bed, in which the titanium hydride powder is treated with a hydrocarbon component at a temperature of 900-1100 ° C and a vacuum of 10 ^-2 -10 ^-3 mm RT.article (R.K. Ognev, A.I. Perevyazko, V.E. Voronkin, V.G. Bryndin, G.G. Kolomoets, Method for producing titanium carbide powder, USSR AS No. 394166, B22f 9/00, C22b 53 / 00 1973, Bull. No. 34). A propane-butane mixture is used as the hydrocarbon component, and titanium hydride in a fluidized bed is treated for 0.5-1 hours. The known method allows to obtain titanium carbide powder with a given carbon content. The authors of this method do not indicate the particle size of the resulting product. However, one skilled in the art will understand that the particle size of the titanium carbide powder obtained by the known method is determined by the particle size of the starting titanium hydride powder. The specialist is clear that the known method does not allow to obtain a titanium carbide nanopowder.

A known method of producing titanium carbide nanoparticles (Shu Watanabe, Keitaroh Nakamura, Method for production of titanium carbide nanoparticles, Patent US 9751769 B2, C01B 31/00, C01B 31/30, H05H 1/30, 2017), in which the powder is titanium or oxide titanium is fed into the flame of the plasma torch, titanium or titanium oxide is vaporized in the plasma torch, the vapor of titanium or titanium oxide is transferred to the reactor and the carrier gas and carbon-containing gas are fed into the reactor. In the reactor, titanium vapor is reacted with a carbon-containing gas and a titanium carbide powder is obtained in which oxygen content is provided. The resulting product — titanium carbide powder with a wide range of particle sizes — is transferred by gas flow to a cyclone separator, where large particles (micron sizes) are separated from it and sent to a separate chamber. The remaining particles are transferred by a vortex gas flow to the collector and trapped in a filter. After sieving large particles, the final product contains titanium carbide particles with an average size of from 1 nm to 100 nm.

In the known method, hydrogen, helium or argon is used as the plasma-forming gas, argon is used as the carrier gas, and methane is used as the carbon-containing gas. The plasma temperature in the known method is 6000-10000 ° C, which is obviously higher than the boiling point of titanium and titanium oxide.

As a source material in the known method using a powder of titanium or titanium oxide with an average particle size of 10-50 microns, either in dry form or in the form of a suspension in a carbon-containing liquid. As the carbon-containing liquid, preferably low molecular weight alcohols are used, such as methanol, ethanol, propanol, isopropyl alcohol.

The known method is intended to obtain titanium carbide nanoparticles with a given oxygen content in the range from 1 to 10 wt. % The oxygen concentration, in turn, is changed by changing the amount of carbon-containing gas in the reactor or by changing the feed rate of the suspension of the original powder.

The known method has a complex technological cycle for the production of titanium carbide, a complex device for its implementation and limited technological capabilities.

The complexity of the technological cycle is associated with the need to obtain high temperatures, prepare suspensions of the starting powders, and separate fractions of particles of the resulting product.

The implementation of the known method requires a complex installation design, which includes a plasma torch for generating plasma, a device for preparing a suspension of starting materials, containers for starting materials, devices for spraying the source material into the plasma torch, a chamber for producing particles of titanium carbide, a pipe for carrying particles of titanium carbide from chambers, a cyclone for separating coarse particles, a collector of coarse particles, a pipeline and a cyclone for entraining the remaining particles in the collection of nanoparticles.

The known method allows to obtain titanium hydride powder of inhomogeneous particle size distribution in batches depending on the capacity of the containers for the source material, but does not allow to obtain nanopowder with an average size of less than 30 nm in a continuous mode, which limits its technological capabilities.

The known method allows to obtain titanium carbide nanoparticles containing oxygen with a given concentration, but does not allow to obtain titanium carbide nanopowders without oxygen impurities, which narrows the scope of its application and limits the technological capabilities of the known method.

The use of titanium and titanium oxide powders with a limited average particle size as starting material also limits the technological capabilities of the method.

The problem to which the invention is directed, is to simplify the technological cycle of obtaining titanium carbide nanopowder, expand the technological capabilities of the method for producing titanium carbide nanopowder and expand its field of application.

The technical result of the invention is expressed in simplifying the production cycle and providing a continuous process for producing titanium carbide nanopowders.

The technical result of the invention is expressed in obtaining a TiC nanopowder in a free-bulk state in the form of particles with an average size of less than 30 nm and thereby expanding the technological capabilities of the method and its field of application.

The technical result of the invention is also expressed in obtaining a titanium carbide nanopowder with an adjustable ratio of titanium and carbon and thereby expanding the technological capabilities of the method and its scope.

The technical result of the invention is also expressed in the production of titanium carbide nanopowder without the content of extraneous elements, in particular, halogens and oxygen, and thereby expanding the technological capabilities of the method and its field of application.

The technical result is achieved by the method of producing titanium carbide nanopowder, in which, according to the invention, in a vertically oriented reactor with a countercurrent inductor, a continuous downward laminar flow of carrier gas is organized, a titanium wire is fed from above into the high-frequency field of the countercurrent inductor, the titanium wire is heated in a high-frequency field to its temperature melting and forming at its end drops, suspend a drop of molten titanium in the space between the turns of countercurrent induction ctor, evaporate titanium from the surface of the molten droplet, provide the entrainment of metallic titanium vapor from the molten droplet, their condensation into nanoparticles and the removal of hot titanium nanoparticles into the reaction zone, a carbon-containing gas is introduced into the reaction zone, and carbon is reacted with titanium in titanium nanoparticles in the reaction zone, ensure the entrainment of freshly formed titanium carbide nanoparticles into the cooling zone downstream, after which titanium carbide nanoparticles are captured by a filter.

The implementation of the inventive method for producing titanium carbide nanopowder is shown schematically in FIG. 1. A continuous downward laminar flow of carrier gas 2 is fed into a reactor 1 made of a transparent heat-resistant dielectric material, for example, quartz or Pyrex glass. A titanium wire is introduced from above into the reactor 1, and it is heated in the high-frequency field of the countercurrent inductor 3 to the melting temperature receive at its end a drop of 4 molten titanium, contactlessly suspend it inside the reactor in the region between the turns of the countercurrent inductor and ensure the evaporation of metallic titanium from the surface drops. The carrier gas stream continuously carries titanium vapor from droplet 4, provides vapor condensation in titanium nanoparticles in the condensation zone 5 below the droplet. The carrier gas stream carries titanium nanoparticles into the reaction zone 6 downstream, into which the carbon-containing reagent gas 7 is supplied through the leakage 8. In the reaction zone 6, the carbon-containing reagent gas 7 interacts with titanium metal in titanium nanoparticles and titanium carbide nanoparticles are obtained. The carrier gas stream carries titanium carbide nanoparticles from the reaction zone downstream to the cooling zone 9, after which it is captured by a filter and a marketable product is obtained in the form of a free-flowing titanium carbide nanopowder.

The metal is replenished in the evaporating drop by continuous supply of titanium wire from above, an inert gas (e.g. argon) is used as the carrier gas, the carbon-containing gas is selected from the class of saturated (alkanes) or unsaturated (alkenes, alkynes) hydrocarbons, and the position of the reaction zone is established. based on the temperature of formation of titanium carbide. The uniformity of the supply of the reagent gas to the reaction zone is ensured by leakage from the leakage into the reactor through the annular gap. The position of the reaction zone is regulated by the position of the annular gap relative to the droplet.

The implementation of the proposed method for producing nanopowder of titanium carbide is illustrated by the following figures.

FIG. 1. Scheme of a device for producing nanopowder of titanium carbide. 1 - a reactor in the form of a tube of dielectric material, 2 - carrier gas flow, 3 - countercurrent high-frequency inductor, 4 - drop of molten titanium, 5 - titanium vapor condensation zone, 6 - reaction zone (titanium carbide formation area), 7 - input carbon-containing reagent gas, 8 - leak, 9 - cooling zone of titanium carbide nanoparticles.

FIG. 2. Characteristics of the titanium carbide nanopowder obtained by the claimed method under the conditions of Example 1. A is a typical image of titanium carbide nanoparticles in a transmission electron microscope, B is the size distribution of titanium carbide nanoparticles, C is a diffraction pattern of titanium carbide nanopowder.

The achievement of the technical result in the implementation of the proposed method is demonstrated by the following examples.

Example 1

In the implementation of the proposed method, a titanium wire with a diameter of D = 0.63 mm is continuously introduced into the reactor at a speed of 2.27 g / hour. A quartz tube with a nominal internal diameter of 14 mm is used as a reactor. As the carrier gas, argon is used. The absolute pressure of the carrier gas inside the reactor is maintained equal to 0.2 atm., The flow rate of the carrier gas is maintained equal to 2600 norms. cm ³ / min. As a carbon-containing reagent gas, a hydrocarbon from the class of alkynes, acetylene, is used. Acetylene consumption is maintained equal to 1000 norms. cm ³ / min.

The resulting product is a free-flowing nanopowder with an average particle size of <D> = 16 nm. The characteristics of the nanopowder obtained under the conditions of Example 1 are shown in FIG. 2. In the images obtained by transmission electron microscopy, the titanium carbide nanoparticles look isolated from each other and do not show a tendency to stick, clump, or the formation of strong aggregates. According to x-ray phase analysis, the obtained nanopowder is titanium carbide TiC. The peaks of low intensity in the given diffraction pattern belong to the crystalline phase of free carbon, i.e. not bound to titanium atoms. The content of titanium carbide in the nanopowder obtained under the conditions of Example 1 is 96.4 weight. %, the content of free carbon is 3.6 weight. %

Example 2

The inventive method is carried out under the conditions of Example 1, but the flow rate of acetylene is maintained equal to 90 norms, cm ³ / min.

The resulting product is a free-flowing nanopowder with an average particle size of <D> = 19 nm. The characteristics of the nanopowder obtained under the conditions of this example are similar to the characteristics of the titanium hydride nanopowder obtained under the conditions of Example 1. According to x-ray phase analysis, the content of titanium carbide in the nanopowder obtained under the conditions of Example 2 is 95.2 weight. %, the content of free carbon is 4.8 weight. %

Examples 1 and 2 show that a change in acetylene consumption by more than an order of magnitude (11 times), ceteris paribus, does not significantly affect the stability of the process for producing titanium carbide nanopowder, reproducibility of the results, and characteristics of the resulting titanium carbide nanopowder.

The above examples demonstrate the absence of the need for precise regulation or fixing a certain value of the flow rate of the reagent gas within a wide range of flow rates, which simplifies the process cycle for producing nanopowder of titanium carbide, expanding technological capabilities and the scope of the method.

Example 3

The inventive method is carried out under the conditions of Example 1, but the absolute pressure of the carrier gas inside the reactor is maintained at 0.5 atm., The flow rate of the carrier gas is maintained at 4600 norms. cm ³ / min, and the flow rate of acetylene is maintained equal to 1100 norms, cm / min.

The resulting product is a free-flowing nanopowder with an average particle size of <D> = 29 nm. According to an x-ray phase analysis, the nanopowder obtained in this example contains titanium carbide TiC in an amount of 96.5 weight. % and titanium metal in an amount of 3.5 weight. %, but does not contain free carbon.

Example 3 shows that reducing the pressure of the carrier gas in the reactor eliminates the admixture of free carbon in the resulting product.

The above example demonstrates the ability to adjust the composition of the resulting product by adjusting the pressure of the carrier gas, which expands the technological capabilities and applications of the proposed method.

Example 4

The inventive method is carried out under the conditions of Example 3, but as a carbon-containing reagent gas, a hydrocarbon from the alkane-methane class is used.

The resulting product is a free-flowing nanopowder with an average particle size of <D> = 26 nm. According to an x-ray phase analysis, the nanopowder obtained in this example contains titanium carbide TiC in an amount of 59.7 weight. %, metal titanium in an amount of 39.6 weight. % and titanium hydride in an amount of 0.7 weight. % The composition of the obtained product indicates the formation of titanium carbide in a limited surface layer of titanium nanoparticles and the preservation of the metal core.

Example 4 demonstrates the ability to control the depth of titanium carbide formation by selecting the class of reactant gas. The above example demonstrates the possibility of obtaining titanium carbide nanoparticles with a core-shell structure, which expands the technological capabilities and applications of the proposed method.

Example 5

The inventive method is carried out under the conditions of Example 3, but hydrocarbons from the alkane class — a propane-butane technical mixture GOST 27578-87 (with a propane content of 50 ± 10%) are used as the carbon-containing reagent gas.

The resulting product is a free-flowing nanopowder with an average particle size of <D> = 26 nm. According to x-ray phase analysis, obtained according to Example 5, the nanopowder contains titanium carbide TiC in the amount of 86.6 weight. % and titanium metal in an amount of 13.4 weight. %

Example 5 shows that the replacement of methane with a propane-butane mixture, ceteris paribus, leads to a decrease in the content of titanium metal in the resulting product.

The above example demonstrates the ability to control the content of titanium metal, and thereby the size of the metal core, in titanium carbide nanoparticles by choosing the type of reagent gas, which expands the technological capabilities and applications of the proposed method.

Example 6

The inventive method is carried out under the conditions of Example 1, but as a carbon-containing reagent gas, a technical mixture propane-butane GOST 27578-87 (with a propane content of 50 ± 10%) is used.

The resulting product is a free-flowing nanopowder with an average particle size of <D> = 12 nm. According to an x-ray phase analysis, the nanopowder obtained in this example contains titanium carbide TiC in an amount of 93.3 weight. %, titanium metal in an amount of about 4.7 weight. % and titanium hydride in an amount of 2.0 weight. %

The given Example 6 demonstrates the ability to control the content of titanium metal, and thereby the size of the metal core, in titanium carbide nanoparticles by adjusting the pressure of the carrier gas, which expands the technological capabilities and applications of the proposed method.

The above examples show that the implementation of the proposed method is provided by a simple technological cycle, and thereby demonstrate the solution of the problem and the achievement of the technical result.

The given examples show the expansion of technological capabilities in terms of ensuring the continuity of the process and thereby demonstrate the solution of the task and the achievement of a technical result.

The above examples show the wide technological capabilities of the proposed method in terms of regulating the composition of the resulting product, expanding the scope of the method, and thereby demonstrate the solution of the problem and the achievement of the technical result.

The above examples show the possibility of obtaining titanium carbide nanopowders in a free-bulk state with an average particle size of less than 30 nm and thereby demonstrate the achievement of a technical result.

The above examples show that obtained by the present method, the nanopowder of titanium carbide does not contain extraneous elements, and thereby demonstrate the achievement of a technical result.

Claims (3)

1. A method of producing titanium carbide nanoparticles, including the evaporation of titanium and the interaction of titanium with a carbon-containing gas, characterized in that the evaporation of titanium is carried out from a drop of molten titanium suspended in a high-frequency field in a vertically oriented reactor, the titanium vapor is carried away from the drop by a continuous downward flow of carrier gas carry out the condensation of titanium vapor into nanoparticles in the condensation zone, and the interaction of titanium with a carbon-containing gas is provided in titanium nanoparticles in the reaction zone below p In the flow, titanium carbide nanoparticles are transferred to the cooling zone and the titanium carbide nanoparticles are captured by the filter, while the carbon-containing gas is introduced into the carrier gas stream above the reaction zone, an inert gas is used as the carrier gas, and the mass loss of the evaporated drop of molten titanium is made up for by continuous feeding into her titanium wire. 2. The method according to p. 1, characterized in that as a carbon-containing gas use a hydrocarbon from the class of saturated hydrocarbons - alkanes. 3. The method according to p. 1, characterized in that as a carbon-containing gas use a hydrocarbon from the class of unsaturated hydrocarbons - alkenes, alkynes.

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