RU2496920C1 - Method of preparation of nanomaterials - Google Patents

Abstract

FIELD: nanotechnology.

SUBSTANCE: method comprises influence of the electric discharge on the electrode in the aqueous electrically conductive medium. At that in the aqueous electrically conductive medium with a specific electric conductivity of 0.3-0.7 Ohm/cm at least two electrodes made of different materials are immersed. The chemical composition of one of the electrodes, which is smaller in the contact area with the electrically conductive medium, corresponds to the desired composition of the resulting nanomaterial. To obtain nanomaterial, the said electrode is exposed with an electric discharge with a specific power of 0.1-0.9 kVA/cm² at room temperature and atmospheric pressure, with the formation of a stationary plasma discharge to form the nanomaterial.

EFFECT: simplicity, accessibility of the method, low-cost equipment.

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Description

Technical field

The invention relates to the field of production of nanomaterials from electrically conductive materials that can be used in energy, metallurgy, production of alloyed powder steels, in chemical and biomedical industries, for the manufacture of parts with electrically conductive properties.

State of the art

A known method using concentrated energy flows, for example, by electric arc erosion of a graphite rod with a cross section of 30 ... 160 mm ² at a current density of 80-200 A / cm ² and I = 20-28 V in a helium atmosphere at P = 40-100 torr (patent for the invention RF №2196731, 2000).

A known method of laser ablation of a metal target (Kozlov G.I. "Letters to ISTF", 2003, v. 29, issue 18, p. 88-94). Under the influence of laser irradiation, atoms and clusters evaporate from the surface and then condense them into nanoparticles.

Known methods involve the creation of high temperatures, low pressure, the use of complex, energy-intensive installations.

There is also known a method of exposing a liquid to a sonoplasmic discharge initiated by an ultrasonic field, characterized by volume glow in the entire space between the electrodes immersed in a liquid multiphase medium. The synthesis of nanomaterials in the known method is realized due to the decomposition of such a multiphase medium (Abramov V.O. et al. “Physicochemical processes in a sonoplasmic discharge”, Materials Science, No. 7, 2010). The installation for the sonoplasmic technology for the synthesis of nanomaterials based on the known method (Laboratory of Ultrasonic Engineering, IONH RAS) operates in the frequency range 21.0-26.0 kHz with a burning voltage of sonoplasmic discharge of 30-400V.

Known for the closest, taken as a prototype, a method of producing nanomaterials, including the effect of an electric discharge on an electrode in an aqueous conductive medium, characterized by the use of pulsed electric discharges in aqueous solutions to obtain nanomaterials and using them to purify water (Danilenko NB, etc. " The use of pulsed electric discharges in aqueous solutions to obtain nanomaterials and their use for water purification ”, Nanotechnology magazine No. 4 (8), pp. 81-91).

The reasons that impede the achievement of the technical result indicated below when using known methods include the fact that in the known methods it is necessary to use a high-voltage pulse transformer, an ultrasonic generator with an emitter in the installation, as well as obtaining a multiphase liquid medium, which complicates the process and makes it energy-intensive and expensive.

Disclosure of invention

The task to be solved by the claimed invention is directed is the development of a method of producing nanomaterials that is inexpensive to use, with minimal cost of materials and energy resources.

The technical result of the invention is the formation of a stationary discharge at room temperature and atmospheric pressure, which simplifies the process of obtaining nanomaterials without the use of expensive equipment and materials.

The technical result is achieved by the fact that the method of producing nanomaterials, including the effect of an electric discharge on an electrode in an aqueous conductive medium, according to the invention, at least two electrodes made of different materials are immersed in an aqueous conductive medium with a specific conductivity of 0.3-0.7 S / cm wherein the chemical composition of one of them, which is smaller in area of contact with the electrically conductive medium, corresponds to the required composition of the obtained nanomaterial, and affect the said elec genus electric discharge power density of 0.1-0.9 kW / cm ² at room temperature and atmospheric pressure to form a stationary plasma discharge to form a nanomaterial particles.

Between the totality of features and the above technical result, there is the following causal relationship.

Obtaining nanostructures in an aqueous electrically conductive medium at room temperature and atmospheric pressure from an electrode material whose chemical composition corresponds to the required composition of the obtained nanomaterial excludes the possibility of using expensive energy-consuming equipment and multiphase liquid medium.

For the implementation of the proposed method, inexpensive equipment is required, consisting of a DC power source N> 1.0 kVA, capacitance with an electrically conductive medium - electrolyte, electrodes with a mount, and a smaller electrode in contact with the electrolyte is made of an electrically conductive material, chemical composition which corresponds to the composition of the obtained nanoparticles. So, to obtain nanographite, spectrally pure graphite is used, to obtain silver - a silver electrode, to obtain VK-8 powder (tungsten-cobalt) - a plate from the corresponding alloy, etc. The electrode designed to produce nanoparticles can be of any shape - flat, cylindrical, disk-shaped, etc. The simultaneous immersion of several electrodes designed to produce nanoparticles increases the productivity of the installation. The method does not require the creation of high temperatures, low pressure. Obtaining nanomaterials occurs at room temperature (18-22 ° C) and atmospheric pressure.

An electrically conductive medium (electrolyte) can be created on the basis of acid, alkali or salt.

Brief Description of the Drawings

Figure 1 shows the installation diagram for implementing the method of producing nanomaterials. Figure 2 shows a photograph of a stationary plasma discharge. Figure 3 is a photograph of the obtained nanomaterial.

The implementation of the invention

The method of obtaining nanomaterials is as follows. The electrode 1, the chemical composition of which corresponds to the required composition of the obtained nanomaterial, is connected to the negative pole of the power source (not shown), the second, larger electrode 2 is connected to the positive pole of the power source. The electrode 2 is made of an inert material. Both electrodes 1 and 2 are immersed in an electrically conductive medium with a specific conductivity of 0.3 S / cm (electrolyte) 3. The electrodes are immersed in an electrolyte, and the contact area of the electrode 1 with the electrolyte is several times smaller than the contact area of the electrode 2 with this electrolyte. The distance between the immersed electrodes is chosen at least 10 mm. When a voltage of 100-300 V is applied to the installation, due to near-electrode potential drop, microplasma discharges are formed on the electrode 1 (Figure 2), the effect of which causes the release of metal particles (melting, evaporation). During operation of the installation, the average electron energy in the discharge column is 3-5 eV, the gas temperature varies from 300 K to 1700 K, depending on the specific power of the discharge. Pure nanoparticles from the electrolyte are taught by centrifugation or by evaporation.

The use of solutions with an electrical conductivity of less than 0.3 S / cm in an installation requires an increase in the input power due to losses in the resistance of the electrolyte. The use of solutions with an electrical conductivity of more than 0.7 S / cm is technically and economically impractical.

Bringing a specific power of less than 0.1 kVA / cm ² to the installation is not enough to form a stable discharge, and exceeding this power above 0.9 kVA / cm ² leads to the melting of the electrode, therefore, the specific power in the described installation is used in the range of 0.1-0 9 kVA / cm ² .

Examples of execution:

The invention is illustrated by examples of specific performance.

Example 1

Two spectrally pure graphite electrodes with a diameter of 6 mm are immersed in an electrolytic bath filled with a HCl solution with a specific conductivity of 0.55 S / cm to a depth of 5.0 and 50.0 mm, respectively. When voltage U = 100V and current I = 1.8A, which is 0.18 kVA / cm ^{2 of the} specific discharge power, an stationary plasma discharge is formed on the electrode, the action of which on the electrode leads to the formation of graphite nanoparticles with sizes less than 100 nm

Example 2

The first electrode in the form of a 1 cm ² plate of VK-8 alloy, the second electrode in the form of a lead ring with a diameter of 60 mm, is immersed in an electrolytic bath filled with a NaOH solution with a specific conductivity of 0.3 S / cm. At U = 190 V and current I = 3 A, Nsp = 0.57 kVA / cm ² , the sizes of the obtained tungsten-cobalt powder are 3-5 nm.

Figure 2 shows a snapshot obtained on an electron microscope computer EVM-100L. The size of the obtained nanoparticles is 3-5 nm.

Claims (1)

A method of producing nanomaterials, including the effect of an electric discharge on an electrode in an aqueous conductive medium, characterized in that at least two electrodes made of different materials are immersed in an aqueous conductive medium with a specific conductivity of 0.3-0.7 S / cm, while the chemical the composition of one of them, which is smaller in area of contact with the electrically conductive medium, corresponds to the required composition of the obtained nanomaterial, and they are affected by the electric discharge with a specific power 0.1-0.9 kVA / cm ² at room temperature and atmospheric pressure with the formation of a stationary plasma discharge for the formation of nanomaterial.

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