RU2612117C1 - Method for producing aluminium nanopowders - Google Patents

Abstract

FIELD: nanotechnology.

SUBSTANCE: invention relates to obtaining aluminum nanopowder from aluminium electrical wire waste and contains at least 99.5% of aluminium. Lead waste spark erosion dispersion in distilled water at a pulse repetition frequency of 95 - 105 Hz, the voltage across the electrodes 90 - 10 and 65 mcF capacitors, followed by centrifugation to separate the solution of large-sized particles from the nanopowder.

EFFECT: method of producing aluminium nanopowder, which provides reduced energy costs and improves the ecological purity of the process.

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Description

The invention relates to the field of powder metallurgy, in particular to compositions and methods for producing aluminum powder, and can be used to restore worn parts, as an additive in paint and varnish coatings, in the manufacture of car tires, in pyrotechnics, chemistry, energy to obtain hydroreactive mixtures that interact with water with the release of heat and hydrogen, or as a metal fuel in explosive compositions and mixed powders.

Famous brands of aluminum powders of various shapes and sizes are obtained in a variety of ways:

- by spraying a molten metal with compressed gas followed by classification of the spray product, RF patent No. 2026157, 6 IPC B22F 9/08;

- by electric explosion of aluminum wire in a nitrogen gas atmosphere, RF patent No. 2112629, 6 IPC B22F 9/14;

- by means of dry mechanical grinding of an aluminum billet in an inert gas atmosphere in the presence of fat additives, which are products obtained from oil refining, RF patent No. 2108534, 6 IPC F42B 4/00, F42B 4/30;

- by spraying the melt with an inert gas heated to 300-400 ° C, with a melt temperature of 880 ° C, further cooling with an inert gas, RF patent No. 2081733, 6 IPC B22F 9/08, C22C 1/14;

- by obtaining a hydroreacting mixture comprising aluminum powder and nickel-doped magnesium powder, RF patent No. 2131841, 6 IPC C01B 3/08, C01B 6/24.

Known widely used in industry is a method of producing aluminum powders using a protective (inert with respect to aluminum) gas environment — nitrogen with a controlled oxygen content, in which, in order to save nitrogen, its recycling is used in the spraying production cycle [Production and use of aluminum powders. - M.: Metallurgy, 1980, 68 p.]. This method is used in almost all aluminum plants in Russia producing sprayed powders. Along with and simultaneously with powdered powders in these factories, aluminum powders are produced along with powders in ball mills using a protective atmosphere (nitrogen with a controlled oxygen content of 2-8%). The disadvantage of this method is the high consumption of nitrogen and the need to organize its production.

It is known to spray molten aluminum with dried air to obtain large powders containing not more than 50% fractions finer than 50-100 microns. Such a process is explosion-proof if the formation of a dust cloud in the system is excluded, which is achieved by the appropriate spraying conditions and the installation of an oil filter at the end of the production line where dust fractions are controlled. When sifting powders obtained in this way in order to isolate product fractions, it is necessary to use nitrogen with a controlled oxygen content (not more than 12%), since in this operation a dust cloud from powder particles less than 50 microns is formed inside the screen. At the same time, along with obtaining powders, obtaining powder by grinding the powder in ball mills, it is also necessary to use nitrogen with a controlled oxygen content (2-8%).

The disadvantages of the known methods are the high energy intensity of the smelting and spray redistribution and their limited applicability - only to certain types of aluminum billets (wire, shavings, powder).

Closest to the claimed is a method for producing composite nanopowders by electrospark dispersion of aluminum in a dielectric medium, which is used hydroxycarboxylic and dicarboxylic acids, USSR copyright certificate No. 1548950 7 IPC B22F 9/14. A significant difference of the proposed method is that it is not necessary to use solutions of salts and acids, this makes the process cheaper and safer for health. Since during electroerosive dispersion in distilled water no harmful substances are released.

The invention is aimed at solving the problem of obtaining aluminum nanopowders from waste with low cost, low energy costs and environmental cleanliness of the process.

The problem is achieved by the method of producing aluminum nanopowder from waste, which differs from the prototype in that the waste electrical aluminum wire (GOST 14838-78) is subjected to electroerosive dispersion in distilled water at a pulse repetition rate of 95 - 105 Hz; the voltage at the electrodes is 90 - 110 V and the capacitance of the capacitors is 65 μF.

The figure 1 describes the steps for producing aluminum nanopowder; figure 2 is a diagram of the EED process, figure 3 is a photograph of the obtained aluminum powder, figure 4 is a radiograph of aluminum powder, figure 5 (A), (B) and 6 are micrographs of nanoparticles of aluminum powder; in FIG. 5 (B) in table 1 is the phase composition of aluminum powder.

The EED process is the destruction of conductive material as a result of local exposure to short-term electrical discharges between the electrodes [Nemilovi EF Electroerosive processing of materials. - L .: Engineering, Leningrad. Dep., 1983. - 160 p.]. Obtaining aluminum powder in an experimental setup for producing nanodispersed powders from conductive materials [RU Patent for the invention No. 2449859] was carried out according to the scheme shown in figure 1, in four stages:

- 1 stage - preparation for the process of electroerosive dispersion;

- 2 stage - the process of electroerosive dispersion;

- Stage 3 - powder unloading from the reactor and its centrifugation;

- Stage 4 - drying and weighing aluminum nanopowder.

The powder materials obtained in this way are generally spherical and elliptical in particle shape. Moreover, by changing the electrical parameters of the dispersion process (voltage at the electrodes, capacitance of the capacitors and pulse repetition rate), it is possible to control the width and offset of the particle size interval, as well as the performance of the process. A centrifuge is used to separate nanoparticles from large ones.

At the first stage, aluminum waste was sorted, washed, dried, degreased, and weighed. The reactor was filled with a working medium - distilled water, the waste was loaded into the reactor. Mounted electrodes. Mounted electrodes were connected to a generator. The necessary process parameters were set: pulse repetition rate, voltage at the electrodes, capacitor capacitance.

At the second stage - the stage of electroerosive dispersion included installation. The EED process is presented in figure 2. The pulse voltage of the generator 2 is applied to the electrodes 5 and then to the aluminum waste 8 (aluminum waste also serves as the electrodes). When a voltage of a certain value is reached, an electrical breakdown of the working medium 10, located in the interelectrode space, occurs with the formation of a discharge channel. Due to the high concentration of thermal energy, the material at the discharge point melts and evaporates, the working medium evaporates and surrounds the discharge channel with gaseous decomposition products (gas bubble 9). As a result of significant dynamic forces developing in the discharge channel and the gas bubble, droplets of molten material are ejected outside the discharge zone into the working medium surrounding the electrodes and freeze in it, forming droplet-like particles of aluminum nanopowder 7.

At the third stage, the working fluid with the powder is unloaded from the reactor, and the nanoparticles are separated from the large ones using a centrifuge. In this case, large particles settle under the action of centrifugal forces, and nanoparticles remain in solution.

At the fourth stage, the solution is evaporated, dried, weighed, packed, packed, and then analyzed by nanopowder.

This achieves the following technical result: obtaining aluminum nanopowders with particles of the correct spherical shape with low energy costs and environmental cleanliness of the process by electroerosive dispersion (EED).

The method allows to obtain aluminum powders without the use of chemicals, which significantly affects the cost of the powder and avoids contamination of the working fluid and the environment with chemicals.

The average specific energy consumption in the production of aluminum electroerosive powder is 2.3 kg / kW · h, which is lower than other methods for producing aluminum nanopowders. Electroerosive dispersion allows efficient disposal of aluminum waste with low energy costs and environmental frequency of the process and to obtain aluminum nanopowder.

Nanopowder materials obtained by the EED of aluminum waste can be effectively used in the manufacture and restoration of machine parts in various ways, powder is one of the components of cold welding, flux-cored welding wire is also made using powder, aluminum powder is often added to paint coatings, and they immediately acquire several new qualities:

- a beautiful metallic shade;

- resistance to physical factors;

- resistance to aggressive chemicals.

In the automotive industry, in the manufacture of car tires, which allows you to get a more wear-resistant material that can better give off heat. This light metal is resistant to corrosion and has other positive qualities, so the powder made from it is often used for coating steel products. This is carried out using technologies such as plasma surfacing and spraying, and many other areas of industry and the economy. When creating anti-friction additives, nanosized powders are used, since larger particles lead to faster wear of the friction units of machine parts, in addition, large particles are able to settle in oils and coolants and clog filters in engines. When creating catalysts, nanopowders are also used, since with a decrease in the particle size their specific surface area and, consequently, chemical and catalytic activity increase.

Example 1

To obtain aluminum nanodispersed powder in an experimental setup by the method of electroerosive dispersion, we used waste products of GOST 14838-78 aluminum wire, pre-cut to 5 ... 7 cm. The wire was loaded into a reactor filled with a working fluid — distilled water. The following electrical parameters of the installation were used:

- pulse repetition rate 95 ... 105 Hz;

- voltage at the electrodes 90 ... 110 V;

- capacitance of 65 microfarads.

The resulting aluminum powder (Figure 3) was investigated by various methods. The phase analysis of the powder was carried out on a GBC EMMA powder x-ray diffractometer with a camera for high-temperature studies (up to 1600 ° C) (table 1). Based on figure 4, it was found that the main phases in the powder obtained by electroerosive dispersion in distilled water are three-water alumina (Al ₂ O ₃ · 3H ₂ O), aluminum (Al) and aluminum metahydroxide (AlO (OH)).

To study the shape and morphology of the obtained aluminum nanopowder, images were taken on an EOL JSM-6610 scanning electron microscope. Based on Figure 5A (pulse repetition rate 95 Hz; voltage at the electrodes 90 V; capacitor capacitance 65 μF) and 5B (pulse repetition rate 105 Hz; voltage at the electrodes 110 V; capacitor capacitance 65 μF) nanopowder obtained by EED from aluminum waste , mainly consists of particles of regular spherical shape (or elliptical) with inclusions of particles of irregular shape (conglomerates).

Example 2

To obtain aluminum nanodispersed powder in an experimental setup by the method of electroerosive dispersion, we used waste products of GOST 14838-78 aluminum wire, previously cut at 5 ... 7 cm. The wire was loaded into a reactor filled with a working fluid - distilled water. The following electrical parameters of the installation were used:

- pulse repetition rate of 50 Hz;

- voltage at the electrodes 60 V;

- Capacitor capacitance 55 μF.

To study the shape and morphology of the obtained aluminum nanopowder, images were taken on an EOL JSM-6610 scanning electron microscope. On the basis of figure 6, the powder obtained by the EED method from aluminum waste under these conditions is larger, and the dispersion process itself is less efficient.

Example 3

To obtain aluminum nanodispersed powder in an experimental setup by the method of electroerosive dispersion, we used waste products of GOST 14838-78 aluminum wire, previously cut at 5 ... 7 cm. The wire was loaded into a reactor filled with a working fluid - distilled water. The following electrical parameters of the installation were used:

- pulse repetition rate of 150 Hz;

- voltage at the electrodes 160 V;

- capacitance of 65 microfarads.

Under these conditions, the dispersion process is not stable and is explosive.

Claims (1)

A method of producing aluminum nanopowder, characterized in that the waste electrical aluminum wire containing at least 99.5% aluminum is subjected to electroerosive dispersion in distilled water at a pulse repetition rate of 95 - 105 Hz, the voltage on the electrodes is 90 - 110 V and the capacitance of the discharge capacitors 65 μF followed by centrifugation of the solution to separate the large particles from the nanopowder.

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