Method and device for large scale production of nanopowders using a sonoelectrochemical method

Abstract

In the present method for producing nanopowders, the mean particle size and the particle size distribution of the nanopowders is regulated by means of a controlled increase in the uniformity of the density distribution of cavitation events both in the interior of a galvanic bath and on the surface of a cathode, which is achieved by simultaneously sonicating an electrolyte solution with ultrasonic oscillations having two different frequencies, one of which is at least an order higher than the other. The uniformity of distribution is controlled by adjusting the values of the sound pressure levels of low-frequency and high-frequency ultrasonic oscillations in a reaction medium. A device for carrying out the claimed method comprises a galvanic bath equipped with at least one of a cathode and an anode. The bath is configured in the form of a rectangular hollow prism, the base of which is inclined relative to the side faces thereof. The cathode is provided with ultrasonic transducers and is a high-frequency ultrasonic emitter. The base is an emitter of low-frequency ultrasonic oscillations.

Description

[0001] Method and device for the production of nanopowders by sonoelectrochemical method on an industrial scale

[0002] Field of technology

[0003] The present invention relates to a method for producing nanopowders of transition metals, simple and complex oxides, as well as certain other compounds of transition metals.

[0004] Prior art

[0005] Nanopowders are the fundamental building blocks of nanotechnology. They are widely used in catalysis, biomarkers, photonics, optoelectronics, data storage devices, solar cells, the production of magnetic ferrofluids, and other applications. The physical and chemical properties of metal nanoparticles, metal oxides, and other compounds are primarily determined by their size, particle size distribution, shape, crystallinity, and structure. By varying any of these parameters, the properties of nanopowders can be controlled. Controlling these parameters is crucial for exploiting the size- and particle size-dependent properties of nanopowders.

[0006] Nanopowders are produced by a wide range of methods such as laser ablation, plasma deposition, vapor nucleation, microwave-assisted hydrothermal synthesis, thermal decomposition of organometallic compounds, sonolysis, electrolysis, and chemical methods such as the reduction of salts of the corresponding metals in the presence of a stabilizing agent, or hydrothermal sol-gel synthesis.

[0007] Physical methods, including laser ablation, plasma deposition, and vapor nucleation, can produce virtually all types of metal nanoparticles, but precise size control is difficult.

[0008] Typically, controlled synthesis of nanoparticles is often accomplished using chemical methods, where the size, shape, and composition of these particles can be precisely tuned. However, chemical methods employ high temperatures, organic solvents, and reducing agents, which are highly reactive and pose potential environmental and biological hazards. Some chemical methods require expensive precursors and numerous purification processes, which are more difficult to implement on an industrial scale.

[0009] The production of nanopowders by electrolysis is well known. Electrochemical reduction can produce nanopowders of all transition metals and some alloys, as well as simple and complex transition metal oxides. The latter are produced by oxidizing metal nanopowders formed during the reduction process using an added oxidizer or atmospheric oxygen. Nanopowders are produced from aqueous and / or nonaqueous electrolyte solutions; the source of metal ions can be either sacrificial anodes or salts or other high-purity metal compounds contained in the electrolyte solution. This method has certain advantages over other nanopowder production methods: inexpensive equipment, a single-stage, environmentally friendly process, and high product purity. However, electrochemical nanopowder production is difficult to control particle size and size distribution by appropriately selecting process parameters.Another disadvantage of electrochemical processes for the production of nanopowders is low productivity, despite the fact that electrochemical processes are generally highly productive, such as the copper refining process.

[0010] It should be noted that some publications describe methods for producing metal nanopowders, such as silver, that allow for the production of spherical nanopowders with controlled particle sizes. [1] describes the synthesis of powders ranging from 50 to 200 nm in size by electrolysis. This utilizes a rotating cathode of a special shape, and the silver ions formed by oxidation of the sacrificial anode are reduced by a reducing agent (hydrazine) rather than on the cathode surface. However, the limited volume of the reactor quickly becomes saturated with already formed metal particles, which alters the initial electrolysis conditions, and the amount of reducing agent is limited. This and similar methods and apparatus cannot be used for large-scale nanopowder production.

[0011] Ultrasonic processing in an electrochemical system offers significant advantages over simple electrochemical processes. A method and apparatus for producing ultrafine powders are known, according to a patent [2]. According to this method and apparatus for producing ultrafine powders, widely known as the pulsed sonoelectrochemical method, electrodes are immersed in an electrolytic bath containing elements intended for powder formation in an electrolyte solution. The cathode serves as a concentrator for the ultrasonic emitter, and the anode is an inert plate. A pulsed electrolytic current is generated between the electrodes, and ultrasonic waves are emitted from the cathode, with the electrochemical and ultrasonic pulses alternating.

[0012] Another, somewhat different method for producing nanopowders [3,4] is continuous electrosynthesis using ultrasound, the so-called continuous sonoelectrochemical method. Under continuous ultrasonication, electrochemically synthesized nanoparticles grow to a certain size and are continuously expelled into the electrolyte solution.

[0013] The sonoelectrochemical method (both pulsed and continuous) produces monodisperse nanopowders of metals and certain alloys, simple and complex metal oxides, and other compounds, such as transition metal chalcogenides, with a narrow particle size distribution. The shape, size, and morphology of the resulting nanoparticles are tuned by adjusting operating parameters such as ultrasound power, applied current and electrode potential, ultrasound treatment and current pulse duration, pH, temperature, and electrolyte composition.

[0014] The main reason this potentially high-performance method remains at the laboratory level is that, as the cathode surface area and, consequently, the reactor size increase, current technology fails to ensure homogeneity of cavitation events within the galvanic bath, especially on the cathode surface, where metal ions are reduced and powder particles are formed, subsequently displaced into the electrolyte solution. Due to the inhomogeneity of cavitation events, particularly on the cathode surface, the particle size distribution of the produced powder expands, thereby negating the advantage of the method. Furthermore, increasing the cathode surface directly correlates with productivity.

[0015] The present invention is aimed at solving this problem.

[0016] Disclosure of invention

[0017] The objective of the invention is the large-scale production of monodisperse nanopowders using a sonoelectrochemical method with controlled particle sizes and a narrow granulometric distribution. To illustrate the method, we will consider the processes occurring in the electrolyte solution and on the cathode surface under the simultaneous action of an electrochemical potential and ultrasound.

[0018] In the sonoelectrochemical process for producing metal nanopowders, particles form on the cathode surface through spontaneous nucleation. First, metal ions are reduced on the cathode surface, then the atoms migrate across the surface and combine into nuclei (seeds), which grow into larger particles. The time the particles remain on the cathode determines their size: particles that remain longer become larger.

[0019] The ability of a particle to adhere to the cathode likely depends on its size. Ultrasound alters the kinetics of these processes [5]; moreover, ultrasound displaces particles from the cathode into suspension in the electrolyte solution. Several mechanisms exist for particle displacement, and the primary mechanism is a strong local shock wave (cavitation shock) from the destruction (or collapse) of the cavitation cavity [6]. Consequently, there must be a critical size at which particles are ultimately displaced under the influence of a cavitation shock of a certain strength. This critical size obviously correlates with the energy of the cavitation cavity's collapse.

[0020] Regardless of whether the cathode emits ultrasound or not, cavitation events both within the galvanic bath and on the cathode surface are highly non-uniform, which is one of the reasons for the wide dispersion of particles displaced into the electrolyte solution. The larger the cathode surface area, the greater the non-uniformity, and a large cathode surface area is essential for performance.

[0021] One of the objectives of the method and the device implementing this method, according to the present invention, is the production of monodisperse nanopowders by the sonoelectrochemical method with controlled particle sizes and a narrow granulometric composition in the range of 2-100 nm.

[0022] Another objective of the method and the device implementing this method, according to the present invention, is large-scale production, i.e. commercialization of the sonoelectrochemical method for synthesizing monodisperse nanopowders with a narrow granulometric composition of transition metals, nanopowders of simple and complex oxides of transition metals, as well as nanopowders of some other compounds of transition metals.

[0023] The essence of the invention is a method for producing nanopowders by a sonoelectrochemical method, including regulating the average particle size and granulometric composition of the nanopowders by controlled increase in the uniformity of the distribution of the density of cavitation events both in the space of the galvanic bath and on the surface of the cathode by insonifying the electrolyte solution simultaneously with ultrasonic vibrations of two different frequencies and , one of which is significantly (at least an order of magnitude) higher than the other, wherein the geometry of the galvanic bath includes such a mutual arrangement of the cathode(s) and anode(s), as well as ultrasonic transducers, which contributes to improving the homogeneity of the total sound field in the volume of the electrolyte.

[0024] For example, according to a preferred embodiment of the present invention, the galvanic bath is formed by flat surfaces of cathodes, which are simultaneously high-frequency ultrasonic emitters (fa) and are installed opposite each other at a distance less than the wavelength of low-frequency ultrasound (E), with an inert or sacrificial anode suspended between them, and is provided with a bottom inclined at 10-15 degrees, which is a surface emitting low-frequency ultrasonic vibrations (fa).Moreover, the anode has a multifaceted surface that disperses ultrasonic vibrations of both frequencies, which helps improve the homogeneity of the total sound field in the volume of the electrolyte, as well as the uniformity of the distribution of the density of cavitation events near the surface of the cathode, and the inclined bottom prevents the formation of a standing wave of low-frequency ultrasonic vibrations, or more precisely, minimizes the standing wave ratio (SWR), that is, the ratio of the amplitude of the sound pressure at the antinode (maximum) to the amplitude of the sound pressure at the node (minimum) to approximately one, which also improves the homogeneity of the distribution of the density of cavitation events.

[0025] The aforementioned simultaneous sonication of an electrolyte solution with sound vibrations of two different frequencies intensifies cavitation activity [7], and to a much greater extent than the geometric sum of the cavitation activities when sonicating the electrolyte solution with sound vibrations of these frequencies of the same intensity, but separately [8,9], while the cavitation zone expands. In general, dual-frequency sonication increases the acoustic pressure and simultaneously lowers the cavitation threshold, that is, the minimum sound pressure required for cavitation to occur. Dual-frequency sonication increases the uniformity of the spatial distribution of satellite bubbles

[0010] .

[0026] The population of vigorously oscillating small bubbles arising in a high-frequency field on the surface of the cathode emitter is orders of magnitude larger than the population of cavitating bubbles (bubbles that grow and collapse, generating a localized strong shock wave) arising in a low-frequency ultrasonic field

[0011] . Entering the cavitation zone of a low-frequency field, vigorously oscillating small bubbles acquire the properties of cavitating bubbles, resulting in an increase in both the concentration and the uniformity of the distribution of cavitation events both throughout the volume and on the surface of the cathode.

[0027] The above-mentioned nanopowders include, in particular, transition metal nanopowders, transition metal oxide nanopowders and transition metal chalcogenide nanopowders.

[0028] The above-mentioned average size of the produced nanopowders is adjusted within the range of 2-100 nm by adjusting the amplitude values ​​of the low-frequency and high-frequency ultrasonic vibrations so that where: R н high frequency sound pressure amplitude,

[0029] P L low frequency sound pressure amplitude, where the sound pressure amplitude of at least one of the components cannot be lower than 5-10 4 This is the cavitation threshold for dual-frequency sounding of an electrolyte solution.

[0030] The above-mentioned electrolyte solution may be aqueous, non-aqueous or mixed, single-component or multi-component, and the electrolytes used may be either background electrolytes or compounds containing components of the produced powders, either separately or as mixtures thereof, acids or bases, and the solution may contain surfactants, as well as an antifoaming agent.

[0031] The essence of the invention is also a device for producing nanopowders by a sonoelectrochemical method, containing a galvanic bath equipped with at least one cathode and an anode, wherein the galvanic bath is made in the form of a vertically installed, flattened, rectangular hollow prism, the base of which, which is the bottom of the galvanic bath, is beveled by 10-20 degrees relative to the side ends and is equipped with a tube for removing the product with the liquid phase from the bath for further separation of the product from the liquid phase and processing according to standard methods.The cathode, equipped with ultrasonic transducers and simultaneously being a high-frequency ultrasonic emitter of 200-1000 kHz, is equipped with a heat exchanger for controlling the temperature of the electrolyte solution and forms 80-90% of the surface of at least one of the lateral trapezoidal faces of the galvanic bath, and the bottom, on which low-frequency ultrasonic transducers of 20-40 kHz are mounted, is an emitter of low-frequency ultrasonic vibrations.

[0032] According to one of the preferred embodiments of the present invention, a tubular immersion ultrasonic transducer mounted on the end of a galvanic bath, at the slanted bottom, is used as a source of low-frequency ultrasonic vibrations of 20-40 kHz.

[0033] According to a preferred embodiment of the present invention, the width of the end of the galvanic bath a is less than the wavelength of low-frequency ultrasound, for example, when

[0034] 2 PA0 to t1- c a = — С =21 о 5 о 0 о 0 о = P 7.5 Ecm, and the ratio of the internal dimensions is as follows: end width: width of the side trapezoidal face: height = a: 7a: Pa, with a possible deviation of 5%.

[0035] The performance of an electrochemical reactor is directly dependent on the current. However, excessively high current densities of both cathode and anodic currents during the electrochemical reduction of most transition metals can lead to intensification of secondary electrochemical reactions, such as hydrogen evolution at the cathode, and also lead to severe passivation of both the anode and cathode. For example, if the total cathode area is 4800 cm 2 , with a cathode current density limit of 80 mA / cm 2It is not advisable to use a cathode current greater than 400 A. Considering that the value of the so-called electrochemical equivalent for transition metals is 1-1.2 g / A hour, the productivity of the galvanic bath can reach 400-500 g / hour.

[0036] According to a preferred embodiment of the present invention, the cathode(s) is a rectangular titanium sheet that also serves as a high-frequency ultrasonic emitter. The emitter is constructed as a field of piezoceramic transducers on the titanium sheet, which are framed by corresponding holes in a flat aluminum heat exchanger, the surface of which is tightly joined to the surface of the titanium sheet of the cathode-emitter. The sacrificial or inert anode has a developed surface, for example, in the form of a comb of metal strips, and is suspended in the center of the galvanic bath between the cathodes at a distance of 1 cm using special holders. The comb strips are inclined relative to the cathode surface at an angle of 30-50 degrees.

[0037] According to one of the preferred embodiments of the present invention, in the production of nanopowders of metals, some alloys, as well as simple and complex metal oxides, a sacrificial anode is typically used, with a surface area 1.1-1.5 times greater than the surface area of ​​the cathode(s).

[0038] According to another preferred embodiment of the present invention, an inert anode is used in the production of nanopowders of other metal compounds, such as transition metal chalcogenides.

[0039] The aforementioned electrolyte solution may be aqueous, non-aqueous, or mixed, single-component or multi-component. Preferably, supporting electrolytes are used, which can simultaneously act as stabilizers for the resulting nanoparticles, such as quaternary ammonium or phosphonium salts, as well as corresponding metal compounds—either alone or in mixtures, acids, or bases. The solution may contain surfactants and an antifoaming agent.

[0040] Brief description of graphic materials

[0041] Fig. 1 shows a diagram explaining the method for producing monodisperse nanopowders.

[0042] Fig. 2 is a schematic representation of the proposed device for producing nanopowders with peripheral units.

[0043] Fig. 3 is a schematic representation of one of the preferred embodiments of the proposed device for producing nanopowders.

[0044] Fig. 4 is a schematic representation of another preferred embodiment of the proposed device.

[0045] Fig. 5 shows a schematic representation of a high-frequency ultrasound emitter cathode.

[0046] Fig. 6 shows a section along B-B in Fig. 5 of the high-frequency ultrasound emitter cathode. Fig. 7 shows a schematic representation of a high-frequency ultrasonic Langevin transducer.

[0047] Fig. 8 shows a schematic representation of a high-frequency ultrasonic transducer with a frequency of 1 MHz.

[0048] Fig. 9 is a transmission electron micrograph of zinc oxide powder particles obtained according to the present invention by the procedure described in Example 1.

[0049] Fig. 10 is a transmission electron micrograph of zinc oxide powder particles obtained according to the present invention by the procedure described in Example 2.

[0050] Fig. 11 is a transmission electron microscope image of zinc oxide powder particles obtained according to the present invention by the procedure described in Example 3.

[0051] Implementation of the invention

[0052] Fig. 1 shows a diagram explaining the method for producing monodisperse nanopowders of transition metals, nanopowders of simple and complex oxides of transition metals, and nanopowders of some other compounds. The space of the galvanic bath (1) is formed between the surfaces of the cathodes (2), which are equipped with high-frequency ultrasonic transducers (3) on the back side. From below, the space of the galvanic bath is limited by an inclined bottom (4), on which low-frequency ultrasonic transducers (5) are mounted, wherein the distance between the cathodes is less than the wavelength of low-frequency ultrasonic vibrations, and the design of the bottom (4) as an inclined bottom significantly prevents the formation of a standing wave. A sacrificial or inert anode (6) with a developed surface, for example in the form of a comb of metal strips, is suspended in the center of the galvanic bath between the cathodes at a distance of 1 cm from them, wherein the strips of the comb are inclined relative to the surface of the cathode at an angle of 30-50 degrees.This configuration of the anodes promotes chaotic reflections of ultrasonic vibrations in the space of the galvanic bath (1) filled with an electrolyte solution (7), thereby increasing the degree of diffusion of the sound field, that is, the uniformity of the distribution of sound energy flows.

[0053] The width of the end of the galvanic bath a is less than the wavelength of low-frequency ultrasound, for example, at 2 Pa0 k t!- c a = — С =2 1 о 5 о 0 о 0 р = П 7.5 Есм., and the ratio of the internal dimensions of the galvanic bath is as follows: end width: side width: height = a: 7a: Pa, with a possible deviation of 5%.

[0054] Metal ions contained in the electrolyte solution, or formed as a result of electrochemical oxidation of the sacrificial anode, are reduced on the cathode surface by electrochemical potential. The reduced atoms then migrate across the surface and coalesce into nuclei, which grow into larger particles, which, under ultrasonic influence, are expelled into the electrolyte solution. The time the particles remain on the cathode determines their size. Particles that remain longer become larger, and the primary mechanism for particle displacement is cavitation events—a strong localized shock from the collapse of a cavitation cavity and intense oscillations of small, non-collapsible bubbles near the cathode surface.

[0055] To displace particles of a narrow granulometric composition into the electrolyte solution, both the density and the homogeneity of the distribution of the intensities of cavitation events on the cathode surface are increased by insonifying the electrolyte solution simultaneously with ultrasonic vibrations of two different frequencies f , one of which is at least an order of magnitude higher than the other. On the cathode surface, in the field of a high-frequency ultrasonic emitter fu, pulsating bubbles of small sizes (8) arise, the population of which is several orders of magnitude greater than the population of cavitation bubbles (9) formed in a field of low ultrasonic frequency f

[0011] . Vigorously oscillating small bubbles arising in a high-frequency field, entering the cavitation zone of a low-frequency field, acquire the properties of cavitating bubbles, thereby increasing both the concentration and the uniformity of the distribution of cavitating bubbles both in volume and on the surface of the cathode.

[0056] The granulometric composition of the produced nanopowders is regulated within the range of 2-100 nm by adjusting the values ​​of the sound pressure amplitudes of low-frequency f and high-frequency fn ultrasonic vibrations in such a way that — 1 < Р р Н + P p L < 1, and the amplitude of the sound pressure of the low-frequency component of the sound field should not exceed P L = which significantly reduces the destructive impact ultrasonic cavitation on particles already displaced into the electrolyte solution.

[0057] The particle size distribution of the produced nanopowders, as in prior art, can be controlled by selecting the electrolyte solution composition, temperature, and cathode current density. It is advisable to operate at a current density of less than 80 mA / cm. 2, close to or slightly exceeding the current density limited by diffusion of ions of most transition metals, since too much excess of the current density limited by diffusion leads to intensification of secondary electrochemical reactions, for example, the release of hydrogen.

[0058] The electrolyte solution may be aqueous, non-aqueous or mixed, single-component or multi-component, and the electrolytes used may be background electrolytes, which can simultaneously act as a stabilizer for the resulting nanoparticles, such as quaternary ammonium or phosphonium salts, or compounds containing components of the produced powders - either individually or in mixtures thereof, acids or bases, and the solution may contain surfactants, as well as an antifoaming agent.

[0059] For the production of transition metal nanopowders or transition metal oxides with an average particle size of less than 15 nm, non-aqueous or mixed electrolyte solutions are preferred.

[0060] The performance of any electrochemical process depends on the current strength. Due to the fact that the cathode current density is limited (80 mA / cm 2 ) Productivity directly depends on the cathode area. For example, for a productivity of 1 kg / hour, given that the electrochemical equivalent of transition metals ranges from 0.9 to 1.2 g / Ah, the cathode surface area must be at least 12,500 cm 2 , and the maximum current is 1000 A.

[0061] Fig. 3 and 4 show a schematic representation of a device for producing nanopowders of transition metals, transition metal oxides and transition metal chalcogenides according to the present invention. Fig. 2 shows an image of the proposed device (10) with peripheral units for producing nanopowders, namely with peripheral containers for storing an electrolyte solution (11) and collecting the product (12), mounted on a holder frame (13).

[0062] The device (10) is a metal lined galvanic bath (14) in the form of a flattened, rectangular hollow prism, the base of which is the bottom (15) of the galvanic bath and is beveled at an angle of 10-20 degrees relative to the side ends and is equipped with a tube for removing (16) the product with the liquid phase from the bath for further separation of the product from the liquid phase and processing using standard methods. On the wide side trapezoidal faces of the bath there are rectangular openings (17), covering 80% of the area of ​​the face, along the perimeter of the rectangular openings there are fasteners, bolts (18) and threaded holes (19). In the lower part of the narrow end and shorter face of the galvanic bath there is a check valve (20) for supplying gas to a bubbler (not shown) for bubbling the electrolyte solution, and according to one of the preferred embodiments of the present invention (Fig.4) a low-frequency immersion tubular ultrasonic transducer (21) with a frequency of 20-40 kHz is installed through the lower part of the narrow end and longer edge into the galvanic bath.

[0063] According to another preferred embodiment of the present invention, low-frequency ultrasonic Langevin transducers (22) are mounted on the inclined bottom (15) of the galvanic bath (Fig. 3).

[0064] According to one of the preferred embodiments of the present invention, high-frequency ultrasound emitter cathodes (23), framed by a gasket (not shown) by means of bolts (18) and threaded holes (19), are attached to the side faces of the galvanic bath, closing the openings (17), essentially forming the walls of the galvanic bath.

[0065] According to another preferred embodiment of the present invention, the high-frequency ultrasound emitter cathode (23) is made in the form of a door on hinges (not shown in the drawings), which simplifies maintenance of the device (10).

[0066] A sacrificial or inert anode (24) is suspended by holders (25) through its upper open face in the center of the galvanic bath (14) between the cathodes (23) at a distance of 1 cm from them. The anode (24) is a comb of metal strips, with the strips of the comb inclined relative to the surface of the cathode (23) at an angle of 30-50 degrees. Sacrificial anodes are used primarily for the production of nanopowders of transition metals, some alloys, and simple and complex transition metal oxides, while inert anodes are used primarily for the production of nanopowders of other compounds, such as transition metal chalcogenides.

[0067] Figs. 5 and 6 show a schematic representation of the high-frequency ultrasound emitter cathode (23). This is a polished titanium sheet (26), framed by mounting holes (27), on the back side of which a flat aluminum heat exchanger (28) is tightly joined. The heat exchanger (28) is equipped with a matrix of through holes (29), through which high-frequency ultrasonic transducers (30) are mounted on the back side of the titanium sheet (26). Moreover, high-frequency ultrasonic transducers can be either Langevin transducers (31) for frequencies up to 300 kHz (Fig. 7), or for frequencies from 300 kHz to 1 MHz - thin piezoceramic disks (32), pressed with a certain force to a titanium sheet (26) by means of a bolt (33) through insulator supports (34), fastened to the outer surface of the heat exchanger (28) (Fig. 8).

[0068] Fig. 2 shows one of the variants of the arrangement and configuration of the peripheral containers: a container for storing the electrolyte solution (11) and a container for collecting the product (12), wherein the volume of these containers is at least twice the volume of the galvanic bath of the device. Both containers are provided with drain holes with valves (35), and also have at least three inlet holes. The drain tube (16) of the device (10) is connected via a valve (36) to the container for collecting the product (12), and the immersed tube (37) of the container for storing the electrolyte solution (11) is connected via a valve (38), a tube (39) and an upper open edge to the inner space of the galvanic bath. The space of the container for storing the electrolyte solution (11) and the container for collecting the product (12) are connected by a tube (40) via a valve (41).In addition, one of the inlet openings of the electrolyte solution storage tank is provided with a valve (42) for filling with electrolyte solution, and one of the inlet openings of the product collection tank is provided with a valve (43).

[0069] The electrolyte solution may be aqueous, non-aqueous, or mixed, single-component or multi-component. The electrolytes used include supporting electrolytes, preferably quaternary ammonium or phosphonium salts, primarily for the production of transition metal nanopowders or nanopowders of simple and complex transition metal oxides, as well as compounds containing the components of the powders being produced—either individually or in mixtures—acids or bases, primarily for the production of nanopowders of other metal compounds, such as transition metal chalcogenides. The solution may also contain surfactants and an antifoaming agent. Non-aqueous or mixed electrolyte solutions are preferred for the production of transition metal or transition metal oxide powders with an average particle size of less than 15 nm.

[0070] The device is also equipped with a power supply (not shown in the drawings), which contains adjustable-power low- and high-frequency ultrasonic generators, as well as a DC power source of suitable power. The ultrasonic generator power regulators, paired with the corresponding transducers, are pre-calibrated based on the sound pressure generated by these transducers in a specific galvanic bath. Calibration is performed by measuring the sound pressure distribution with a hydrophone separately for the low- and high-frequency components of the ultrasonic field in the galvanic bath.

[0071] Ultrasonic generators are connected via cables to corresponding high- and low-frequency ultrasound transducers. The negative terminal of the DC power supply is connected to the cathode(s), and the positive terminal is connected to the anode, after the anode is suspended in the galvanic bath.

[0072] The device operates as follows. A sacrificial or inert anode (24), having an appropriate surface area, is secured in a holder (25) and suspended through its upper open face into the device's galvanic bath (10). The positive terminal of a DC power source is connected to the anode (24). A container for storing the electrolyte solution is filled with the electrolyte solution through valve (42).

[0073] The valve (36) connecting the drain tube (16) of the galvanic bath and the product collection container (12) is tightly closed, and the valve (41) on the tube connecting the containers is opened.

[0074] An inert or reactive gas at the desired flow rate falls onto the inlet of the bubbler check valve (20) (not shown in the drawings).

[0075] The electrolyte solution is moved into the galvanic bath by increasing the static pressure above the electrolyte solution in the electrolyte solution storage tank (11) by feeding preferably an inert gas under pressure through the valve (43) of the product collection tank (12) (the inert gas cylinder and compressor are not shown in the drawings), and the galvanic bath is filled to the mark of complete immersion of the cathodes.

[0076] The low- and high-frequency ultrasound generators are alternately switched on from the power supply (44). The desired sound pressure amplitudes of the low- and high-frequency ultrasonic vibrations are set using the ultrasonic generator power regulators calibrated for sound pressure.

[0077] On the power supply (44), a direct current source is switched on, the desired current and voltage values ​​are set, and a direct voltage is dropped on the anode (24) and cathode (23) of the galvanic bath.

[0078] Based on the current value, the electrochemical equivalent of the given metal, and the production time, the weight of the powder already produced is approximately calculated, and when it reaches 3% of the weight of the electrolyte solution contained in the galvanic bath, half of the electrolyte solution containing nanoparticles is drained into the product collection tank (12) by opening the valve (36) connecting the galvanic bath drain tube (16) and the product collection tank (12), while simultaneously opening the valve (43). The electrolyte solution is then added by repeatedly increasing the static pressure above the electrolyte solution in the electrolyte solution storage tank (11).

[0079] And this cycle is repeated the required number of times.

[0080] It should be noted that when the concentration of the synthesized powder is 5-10%, the intensity of cavitation events in the electrolyte changes

[0012] , and significantly, therefore, to be on the safe side, the concentration should not be allowed to be more than 3-4%.

[0081] After completion of the production process, the product is separated from the liquid phase by decantation and filtration, washed and dried using standard methods.

[0082] Below are examples of the production of zinc oxide nanopowder under different conditions of sonication of the electrolyte solution simultaneously at two different frequencies.

[0083] Example 1

[0084] In a galvanic bath with a cathode surface area of ​​4500 cm 2 Zinc anodes (99.7% purity) with a total surface area of ​​5000 cm are suspended on special holders 2 . A 15-liter electrolyte solution is poured in, namely a 1.5 molar solution of tetrabutylammonium bromide in 99.6% methanol.

[0085] Throughout the production process, the temperature of the electrolyte solution is maintained at 36 degrees Celsius by means of a thermostat and heat exchangers on the cathodes.

[0086] Oxygen is supplied to the bubbler inside the device through a check valve at a flow rate of 2 l / min. The low-frequency (20 kHz) and high-frequency (200 kHz) ultrasonic generators on the power supply are alternately activated. Using power regulators, which are pre-calibrated for sound pressure and paired with the corresponding transducers, set the following sound pressure values: for 20 kHz - 80 10 4 and for 200 kHz - 150-10 4 T 2 -

[0087] The DC power supply is turned on and a constant voltage is applied to the anode and cathode. Electrolysis is carried out in galvanostatic mode, with the current set to 150 A and the voltage set to 10 V. The current density is 33 mA / cm. 2The process is maintained for two hours, after which the DC power source and ultrasonic generators are successively disconnected. The bath contents are transferred to a product collection vessel. The product is separated from the liquid phase by decantation and filtration, washed over a filter, and then dried in a drying oven at 70 degrees Celsius. The resulting yield is 315 grams of zinc oxide powder, corresponding to a current efficiency of approximately 90%.

[0088] A transmission electron microscope (FEI Tecnai F30) examination, shown in Fig. 9, shows that the particle sizes are 5-6 nm.

[0089] The specific surface area was analyzed on a Belsorp Mini II under the following conditions:

[0090] Pre-treatment: 120°C, 60 minutes under vacuum, working gas - nitrogen, pressure measurement range: from 0 to 0.95 atm. Result BET 195 m 2 / gr.

[0091] Example 2

[0092] A complete repetition of Example 1 with the only difference that using power regulators, which are pre-calibrated according to sound pressure in a pair with the corresponding converters, the following sound pressure value is set pressures: for 20 kHz - 50 10 4 and for 200 kHz - 98 10 t 4 T

[0093] The resulting yield is 325 grams of zinc oxide powder, which corresponds to a current efficiency of approximately 90%.

[0094] A transmission electron microscope (FEI Tecnai F30) examination, the image of which is shown in Fig. 10, shows that the particle sizes are 10-11 nm.

[0095] Specific surface areas were analyzed on a Belsorp Mini II under the following conditions:

[0096] Pre-treatment: 120°C, 60 minutes under vacuum, working gas - nitrogen, pressure measurement range: from 0 to 0.95 atm. Result BET 102 m 2 / gr.

[0097] Example 3

[0098] A complete repetition of Example 1 with the only difference that using power regulators, which are pre-calibrated for sound pressure in a pair with the corresponding converters, the following sound pressure values ​​are set: for 20 kHz - 30 10 4 and for 200 kHz - 40 10 t 4 The resulting yield is 332 grams of zinc oxide powder, which corresponds to a current efficiency of about 90%.

[0099] A transmission electron microscope (FEI Tecnai F30) examination, the image of which is shown in Fig. 11, shows that the particle sizes are 20-23 nm.

[0100] Specific surface areas were analyzed on a Belsorp Mini II under the following conditions:

[0101] Pre-treatment: 120°C, 60 minutes under vacuum, working gas - nitrogen, pressure measurement range: from 0 to 0.95 atm. Result BET 45 m 2 / gr.

[0102] Sources of information:

[0103] 1. Patent application US 2012 / 0091009A1, published April 19, 2012.

[0104] 2. WO9533871A1, published 14.12.1995, MIC: C25B1 / 00; C25C5 / 00; C25C5 / 02;

[0105] 3. Plaipaite-Nalivaiko R., Griskonis E., Adliene D., Gilys L., Continuous ultrasound assisted sonoelectrochemical synthesis of W-Co alloy nanoparticles. Acta Physica Polonica A. 2019; 136(2):267-273.

[0106] 4. patent KR100555584, published 12 / 17 / 2004, IPC: B22F9 / 16);

[0107] 5. C. G. Jung, F. Chapelle, A. Fontana, Influence of ultrasound on the kinetic parameters of electrochemical redox reactions, Ultrasonics Sonochemistry 4 (1997) 117-120

[0108] 6. Leen van Wijngaarden, Mechanics of collapsing cavitation bubbles, Ultrasonics Sonochemistry 29, (2016), 524-527

[0109] 7. I. I. Khavskiy, Technological effect of simultaneous action of ultrasonic vibrations of different frequencies in liquids, ACOUSTIC JOURNAL Vol. XXV, (1979), Issue 1, pp. 119-123

[0110] 8. A. V. Feldman, I. I. Khavskiy, Increase in the erosive activity of the cavitation region under the combined action of ultrasonic vibrations of different frequency ranges, Dynamic effects of powerful ultrasound, Izhevsk 1981, pp. 9-17

[0111] 9. Ruo Feng, Yiyun Zhao, Changping Zhu, TJ Mason, Enhancement of ultrasonic cavitation yield by multi-frequency sonication, Ultrasonics Sonochemistry 9 (2002) 231-236 10. Justin A. Morton, Mohammadvari and all, Dual frequency ultrasonic cavitation in various liquids: Highspeed imaging and acoustic pressure measurements, Physics of Fluids 35, 017135 (2023)

[0112] 11. Kaouther Kerboua and Oualid Hamdaoui, Void fraction, number density of acoustic cavitation bubbles, and acoustic frequency: A numerical investigation, The Journal of the Acoustical Society of America 146, 2240 (2019)

[0113] 12. Ce Guo, Jing Liu, Xiuhong Li, Shengqiang Yang, Effect of cavitation bubble on the dispersion of magnetorheological polishing fluid under ultrasonic preparation, Ultrasonics Sonochemistry 79 (2021) 105782

Claims

Invention formula 1. A method for producing nanopowders using a sonoelectrochemical method, according to which, in a galvanic bath equipped with an anode, a cathode, and ultrasonic emitters, the average particle size and granulometric composition of nanopowders are regulated by controlled increase in the uniformity of the distribution of the density of cavitation events both in the space of the galvanic bath and on the surface of the cathode by insonifying the electrolyte solution simultaneously with ultrasonic vibrations of two different frequencies, one of which is at least an order of magnitude higher than the other, and the uniformity of the distribution of the density of cavitation events in the space of the galvanic bath and on the surface of the cathode is controlled by adjusting the values ​​of the amplitudes of low-frequency sound pressures (P L ) and high-frequency (P н ) ultrasonic vibrations in the reaction medium.

2. The method according to paragraph 1, characterized in that the said nanopowders are, in particular, nanopowders of transition metals, certain alloys, nanopowders of simple and complex oxides of transition metals and chalcogenides of transition metals.

3. The method according to paragraph 1, characterized in that the average size of the produced powders is regulated within the range of 2-100 nm by adjusting the values ​​of the amplitudes of low-frequency and high-frequency ultrasonic vibrations in such a way that — 1 < - < 1, where r L this is the amplitude of low frequency sound pressure, P н - the amplitude PH+PL of high-frequency sound pressure, and the amplitude of the sound pressure of at least one of the components cannot be lower than 5 10 4 - -. T 2 4. The method according to paragraph 1, characterized in that the electrolyte solution may be aqueous, non-aqueous or mixed, single-component or multi-component, and the electrolytes used may be either background electrolytes or compounds containing components of the produced powders - either separately or as mixtures thereof, acids or bases, and the solution may contain surfactants, as well as an antifoaming agent.

5. A device for producing nanopowders by a sonoelectrochemical method, comprising a galvanic bath equipped with at least one cathode and an anode, wherein the galvanic bath is made in the form of a vertically installed, flattened, rectangular hollow prism, the base of which, which is the bottom of the galvanic bath, is beveled by 10-20 degrees relative to the side ends and is equipped with a tube for removing the product with the liquid phase from the bath for further separation of the product from the liquid phase and processing using standard methods, wherein the cathode, equipped with ultrasonic transducers and simultaneously being a high-frequency ultrasonic emitter of 200-1000 kHz, is equipped with a heat exchanger for controlling the temperature of the electrolyte solution and forms 80-90% of the surface of at least one of the lateral trapezoidal faces of the galvanic bath, and the bottom, on which low-frequency ultrasonic transducers of 20-40 kHz are mounted, is an emitter of low-frequency ultrasonic vibrations.

6. The device according to paragraph 5, characterized in that the galvanic bath is metallic and lined, preferably with fluoroplastic.

7. The device according to paragraph 5, characterized in that the width of the end of the galvanic bath a is less than the wavelength of low-frequency ultrasound, and the ratio of the internal dimensions is as follows: end width : width of the lateral trapezoidal face : height = a : 7a : Pa, with a possible deviation of 5%.

8. The device according to paragraph 5, characterized in that in the production of nanopowders of metals, some alloys, as well as simple and complex metal oxides, a sacrificial anode is used, which has a developed surface equipped with ribs or spikes, for example a comb of metal strips, and the surface area of ​​the anode is 1.1 - 1.5 times greater than the surface area of ​​the cathode (cathodes).

9. The device according to paragraph 5, characterized in that in the production of nanopowders of other metal compounds, for example transition metal chalcogenides, when the raw materials are components of an electrolyte solution, anodes with a developed surface provided with ribs or spikes are used, for example a comb of strips of metal, a material inert with respect to the electrolyte solution.

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