RU2432231C2 - Method of producing metal nano-sized powders - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to production of metal nano-sized powders. Proposed method comprises heating initial metal in inert gas flow to initial metal evaporation temperature and extracting metal powder from said flow at temperature lower than that of initial metal fusion point. Initial metal is heated by electron beam with energy of 0.4-3.0 MeV and power not lower than 200 kW at pressure approximating to atmospheric pressure and inert gas flow rate making 0.5-25000 l/min.

EFFECT: industrial production of high-purity metal nanopowders.

12 cl, 2 dwg, 9 ex

Description

The invention relates to technologies for the production of metal powders having a fraction size expressed in nano units and can be used to produce powders of pure metals: iron, copper, nickel, cobalt, tungsten, molybdenum and other elements, as well as metal alloys in the chemical industry, powder metallurgy and other industries.

Currently, metal nanosized powders are obtained mainly in two ways: chemical, including precipitation in aqueous solutions and reduction of the powder from metal oxides and hydroxides, and physical, including the evaporation of the metal and its subsequent condensation.

For example, a chemical method for producing metal nanosized powders is known, based on the reaction for producing metal hydroxides with their subsequent dehydration and reduction [Gavrilov OS, Volkogon G.M. et al. “Technological process for producing metal nanopowders by the chemical-metallurgical method”, First International Forum on Nanotechnologies, 2008, http://newrusnano.explosion.ru/]. In accordance with this method, metal salts: chlorides, sulfates, sulfides, after sifting and, if necessary, crushing, are pre-dissolved in water and then a solution of the reagent Na hydride is fed into the salt solution in an even thin layer in order to ensure the optimal flow of the corresponding hydroxide formation reaction metal. Next, the resulting suspension is filtered and subjected to dehydration in a drying unit. The final stage - the reduction of metal hydroxides to metal nanosized particles - is carried out in an electric furnace at a temperature of 1000 ° C. For the purpose of passivation, the resulting powder is placed in a nitrogen atmosphere.

A known method of producing nickel powder by reducing basic nickel carbonate in an aqueous medium at a temperature of 80-90 ° C, in accordance with which the restoration is carried out with an aqueous solution of hydrazine hydrate with a hydrazine concentration of at least 4 mol / l with a molar ratio of hydrazine to nickel of at least 1 , 3 [RF Patent No. 2102191].

A known method of producing nanosized powders of iron, copper, nickel, cobalt, tungsten, molybdenum and metal alloys, which includes chemical precipitation of at least one metal hydroxide with an alkali solution to form a suspension, diafiltration of the resulting suspension with separation of the solution of at least one metal hydroxide , its dehydration, preheating of at least one metal hydroxide and its reduction to obtain a metal powder and the subsequent passivation of the specified powder, When this diafiltration is carried out simultaneously with the purification sorption slurry and reduction of the metal hydroxide and passivation of the metal powder is carried out under vigorous stirring of the material [RF patent №2170647]. The method allows to obtain a nanoscale metal powder with a structure of particles having a low level of distortion and the absence of extended defects, as well as a high-purity metal powder consisting of particles of a monodisperse state while maintaining a narrow fractional composition and a given morphology, and provides the ability to control dispersion at all stages of the technological process.

A known method of producing nanoscale metal powder, comprising causing a plasma discharge in water at high pressure between two electrodes, one of which is made of elemental metal. Plasma discharge is carried out in such a way as to cause the evaporation of metal ions and contacting the formed vapor with water in order to turn metal ions into metal powder [US Patent No. 7300491]. In this way, powders of titanium, zirconium, germanium, tin, gold, silver or platinum are obtained.

A known method of producing nanostructured metal powder, which use a metal wire as a source of metal, two wires as electrodes; between which an electric arched discharge is carried out in order to melt the ends of the metal wire and obtain a melt, which is converted into droplets by a spray device, the temperature being maintained between the melting point and the boiling point in order to avoid evaporation of the droplets. Drops of metal are quenched by cooling in a cyclone device so that each drop immediately solidifies, forming a nanoscale sphere [US Patent No. 7431750].

A known method of producing a metal nanosized powder, comprising melting a metal having the form of a wire by an electric arc discharge, forming drops of molten metal in a special device and cooling, the temperature of the arc discharge being maintained in such a way as to avoid evaporation of the metal, and cooling is carried out in the device in such a way so that the metal droplets instantly solidify to form a spherical powder with a particle size of approximately 500 nm [US Patent No. 734157].

A known method of producing nanosized metal powders, in accordance with which the metal is evaporated by heating it in an evaporator having the form of a tubular furnace. In this case, an inert gas stream is passed through the evaporator, which traps and carries metal vapor from the evaporator. Then the inert gas is quickly cooled - quenched in a water tubular heat exchanger, as a result of which the metal vapor turns into a metal powder with a nanoscale fraction [K.Wegner, B. Walker, S. Tsantilis, S. Pratsinis “Design of metal nanoparticle synthesis generation flow condensation "Chemical Engineering Science No. 57, 2002]. This method is the closest analogue of the proposed method and adopted as a prototype of the invention.

The disadvantage of the prototype is its low productivity, which prevents the production of metal nanoscale powders on an industrial scale. In addition, the furnace walls at high temperatures can release ions of materials that pollute the atmosphere and the final product is metal powder.

The invention solves the problem of creating a method for producing metal nanoscale powders, which allows to obtain such powders on a large scale and provides high purity of the obtained metal nanoscale powders.

The problem is solved in that a method for producing a metal nanoscale powder is proposed, comprising heating the source metal in an inert gas stream to the temperature of evaporation of the source metal with the formation of metal vapor in the inert gas stream and recovering the metal powder from the inert gas stream at a temperature below the melting temperature of the source metal , in which the heating of the source metal is carried out by an electron beam having an energy of 0.4-3 MeV and a power of not more than 200 kW, at a pressure close to atmospheric, and an inert gas flow rate of 0.5-25000 l / min.

The electron beam is mainly generated by an electron accelerator.

As the inert gas, any of the known inert gases can be used, for example argon, helium, neon, krypton, xenon, carbon dioxide, or a mixture thereof.

The inert gas flow rate depends on the source metal, its boiling point, energy and power of the electron beam.

As the metal can be used metals belonging to I, II, III, IV, V, VI, VII, VIII groups of the Periodic table, namely:

Group I - copper (Cu), silver (Ag), gold (Au);

Group II - beryllium (Be), magnesium (Mg), calcium (Ca), zinc (Zn), strontium (Sr), cadmium (Cd), barium (Ba), radium (Ra);

Group III - aluminum (Al), scandium (Sc), gallium (Ga), yttrium (Y), indium (In), lanthanum (La), including cerium (Ce) lanthanides, praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium - (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) lutetium (Lu); including from actinides, thorium (Th) and uranium (U);

Group IV - silicon (Si), titanium (Tl), germanium (Ge), zirconium (Zr), tin (Sn), hafnium (Hf), lead (Pb);

V group - vanadium (V), niobium (Nb), antimony (Sb), tantalum (Ta), bismuth (Bi);

Group VI - chromium (Cr), molybdenum (Mo), tungsten (W), polonium (Po);

VII group - manganese (Mn), technetium (Tc), rhenium (Re);

Group VIII - iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt).

To obtain a powder from a metal alloy, at least two metals that are heated together are used as the starting metal.

Figure 1 shows the appearance of the nanosized silver powder obtained by implementing the method, and figure 2 shows the appearance of the obtained nanosized tungsten powder.

The proposed method is as follows.

The solid source material - metal in the form of a monolith or large pieces - is placed in the evaporation chamber and a concentrated electron beam with an energy of 0.4-3 MeV and a power of not more than 200 kW, the values of which depend on the boiling temperature of the treated metal, is sent to its surface. A concentrated electron beam generates an electron accelerator. As a result of exposure, at least a portion of the metal of the surface to be treated passes into a vaporous state. Simultaneously with the action of an electron beam on the metal surface, an inert gas is supplied to the evaporation chamber, maintaining the pressure in the evaporation chamber close to atmospheric pressure. The inert gas flow has a flow rate in the range of 0.5-25000 l / min and depends on the melting temperature of the metal and the power of the electron beam. The inert gas stream captures particles of metal vapor - molecules and ions in the vapor-gas state, and carries them away from the evaporation zone. Since the temperature of the inert gas is lower than the temperature at the melting point of the starting metal, metal powder is precipitated already in the inert gas stream and rapidly solidifies. Therefore, the gas flow can be directed from the evaporation chamber either to the cooling chamber, or directly to the storage hopper.

This method allows to obtain nanosized powders on an industrial scale due to the high productivity of the electron beam and the powders are of high purity, since no foreign inclusions enter the inert gas atmosphere.

Example 1

A sample of metal - silver, belonging to group I of the Periodic table, is placed in the evaporation chamber. An inert argon gas is supplied to the evaporation chamber in the form of a stream moving at a rate of 0.5-50 liters per minute. The metal surface is affected by an electron beam from an electron accelerator with a power of 5-130 kW. Under the influence of an electron beam, the surface heats up to the temperature of vaporization. Silver vapors are formed, which are captured by a stream of inert gas and together with it move to the exit of the evaporation chamber. Since the temperature of the inert gas is lower than the melting point of silver, nanosized silver powder is deposited from silver vapor. The nanosized powder is carried away by a stream of inert gas into the storage hopper, where it is naturally cooled. The result is powders with average nanoparticle sizes from 5 to 200 nanometers (FIG. 1) with a capacity of up to two kilograms per hour.

Example 2

A sample of metal - zinc, belonging to group II of the Periodic table, is placed in an evaporation chamber. An inert argon gas is supplied to the evaporation chamber in the form of a stream moving at a flow rate of 0.5-20 liters per minute. A metal beam is applied to the metal surface from an electron accelerator with a power of 5-50 kW. Under the influence of an electron beam, the surface heats up to the temperature of vaporization. Zinc vapor forms, which are captured by a stream of inert gas and with it move to the exit of the evaporation chamber. Since the temperature of the inert gas is below the melting point of zinc, nanosized zinc powder precipitates from zinc vapor. The nanosized powder is carried away by a stream of inert gas into the storage hopper, where it is naturally cooled. The result is powders with average nanoparticle sizes from 15 to 100 nanometers with a capacity of up to twenty kilograms per hour.

Example 3

A sample of metal - aluminum, belonging to group III of the Periodic table, is placed in the evaporation chamber. An inert argon gas is supplied to the evaporation chamber in the form of a stream moving at a flow rate of 1-30 liters per minute. A metal beam is applied to the metal surface from an electron accelerator with a power of 5-100 kW. Under the influence of an electron beam, the surface heats up to the temperature of vaporization. Vapors of aluminum are formed, which are captured by the inert gas flow and together with it move to the exit of the evaporation chamber. Since the temperature of the inert gas is lower than the melting point of aluminum, nanosized aluminum powder precipitates from aluminum vapor. The nanosized powder is carried away by a stream of inert gas into the storage hopper, where it is naturally cooled. The result is powders with average nanoparticle sizes from 10 to 250 nanometers with a capacity of up to eight kilograms per hour.

Example 4

A sample of metal - titanium, belonging to group IV of the Periodic table, is placed in an evaporation chamber. An inert argon gas is supplied to the evaporation chamber in the form of a stream moving at a rate of 1-40 liters per minute. A metal beam is applied to the metal surface from an electron accelerator with a power of 5-150 kW. Under the influence of an electron beam, the surface heats up to the temperature of vaporization. Titanium vapors are formed, which are captured by a stream of inert gas and together with it move to the exit of the evaporation chamber. Since the temperature of the inert gas is below the melting point of titanium, nanosized titanium powder is deposited from titanium vapor. The nanosized powder is carried away by a stream of inert gas into the storage hopper, where it is naturally cooled. The result is powders with average nanoparticle sizes from 20 to 300 nanometers with a productivity of up to two kilograms per hour.

Example 5

A sample of tantalum metal belonging to group V of the Periodic Table is placed in an evaporation chamber. An inert argon gas is supplied to the evaporation chamber in the form of a stream moving at a rate of 1-50 liters per minute. The metal surface is affected by an electron beam from an electron accelerator with a power of 20-200 kW. Under the influence of an electron beam, the surface heats up to the temperature of vaporization. Tantalum vapors are formed, which are captured by a stream of inert gas and with it move to the exit of the evaporation chamber. Since the temperature of the inert gas is lower than the melting point of tantalum, nanosized tantalum powder precipitates from tantalum vapors. The nanosized powder is carried away by a stream of inert gas into the storage hopper, where it is naturally cooled. The result is powders with average nanoparticle sizes from 40 to 100 nanometers with a productivity of up to one kilogram per hour.

Example 6

A metal sample of tungsten belonging to group VI of the Periodic table is placed in an evaporation chamber. An inert gas helium is supplied to the evaporation chamber in the form of a stream moving at a rate of 0.5-50 liters per minute. The surface of the metal is affected by an electron beam from an electron accelerator with a power of 10-200 kW. Under the influence of an electron beam, the surface heats up to the temperature of vaporization. Tungsten vapors are formed, which are captured by a stream of inert gas and together with it move to the exit of the evaporation chamber. Since the temperature of the inert gas is lower than the melting point of tungsten, nanosized tungsten powder is deposited from tungsten vapor. The nanosized powder is carried away by a stream of inert gas into the storage hopper, where it is naturally cooled. The result is powders with average nanoparticle sizes from 5 to 300 nanometers (FIG. 2).

Example 7

A sample of metal - rhenium, belonging to group VII of the Periodic table, is placed in the evaporation chamber. An inert argon gas is supplied to the evaporation chamber in the form of a stream moving at a rate of 1-40 liters per minute. A metal beam is applied to the metal surface from an electron accelerator with a power of 25-200 kW. Under the influence of an electron beam, the surface heats up to the temperature of vaporization. Rhenium vapor forms, which are captured by a stream of inert gas and together with it move to the exit of the evaporation chamber. Since the temperature of the inert gas is lower than the melting point of rhenium, nanosized rhenium powder is deposited from rhenium vapor. The nanosized powder is carried away by a stream of inert gas into the storage hopper, where it is naturally cooled. The result is powders with average nanoparticle sizes from 30 to 200 nanometers with a capacity of up to one kilogram per hour.

Example 8

A sample of metal - Nickel, belonging to group VIII of the Periodic table, is placed in the evaporation chamber. An inert argon gas is supplied to the evaporation chamber in the form of a stream moving at a rate of 0.5-50 liters per minute. The metal surface is affected by an electron beam from an electron accelerator with a power of 20-200 kW. Under the influence of an electron beam, the surface heats up to the temperature of vaporization. Nickel vapors are formed, which are captured by a stream of inert gas and together with it move to the exit of the evaporation chamber. Since the temperature of the inert gas is lower than the melting point of nickel, nanosized nickel powder is deposited from nickel vapor. The nanosized powder is carried away by a stream of inert gas into the storage hopper, where it is naturally cooled. The result is powders with average nanoparticle sizes from 20 to 200 nanometers with a productivity of up to two kilograms per hour.

Example 9

An alloy sample of titanium nickelide is placed in an evaporation chamber. An inert gas helium is supplied to the evaporation chamber in the form of a stream moving at a rate of 0.5-50 liters per minute. The metal surface is affected by an electron beam from an electron accelerator with a power of 20-200 kW. Under the influence of an electron beam, the surface heats up to the temperature of vaporization. A pair of elements are formed that make up the alloy, which are captured by a stream of inert gas and together with it move to the exit of the evaporation chamber. Since the temperature of the inert gas is lower than the melting point of titanium and nickel, a nanosized alloy powder, titanium nickelide, is deposited from the vapor. The nanosized powder is carried away by a stream of inert gas into the storage hopper, where it is naturally cooled. The result is powders with average nanoparticle sizes from 50 to 300 nanometers with a productivity of up to one kilogram per hour.

Claims (12)

1. A method of producing a metal nanoscale powder, comprising heating the source metal in an inert gas stream to a vaporization temperature of the source metal to form metal vapor in an inert gas stream and recovering metal powder from the inert gas stream while cooling the metal vapor to a temperature below the melting temperature of the source metal, characterized in that the heating of the source metal is carried out by an electron beam having an energy of 0.4-3 MeV and a power of not more than 200 kW, at a pressure close to ohm to atmospheric, and an inert gas flow rate of 0.5-25000 l / min. 2. The method according to claim 1, characterized in that the electron beam is generated by an electron accelerator. 3. The method according to claim 1, characterized in that the inert gas is argon, or helium, or neon, or krypton, or xenon, or carbon dioxide, or a mixture thereof. 4. The method according to claim 1, characterized in that the source metal is selected from the range: copper, silver, gold. 5. The method according to claim 1, characterized in that the source metal is selected from the series: beryllium, magnesium, calcium, zinc, strontium, cadmium, barium, radium. 6. The method according to claim 1, characterized in that the source metal is selected from the series: aluminum, scandium, gallium, yttrium, indium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, thorium, uranium. 7. The method according to claim 1, characterized in that the source metal is selected from the series: silicon, titanium, germanium, zirconium, tin, hafnium, lead. 8. The method according to claim 1, characterized in that the source metal is selected from the series: vanadium, niobium, antimony, tantalum, bismuth. 9. The method according to claim 1, characterized in that the source metal is selected from the range: chromium, molybdenum, tungsten, polonium. 10. The method according to claim 1, characterized in that the source metal is selected from the series: manganese, technetium, rhenium. 11. The method according to claim 1, characterized in that the source metal is selected from the series: iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum. 12. The method according to claim 1, characterized in that the source metal is at least two metals that are heated together.

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