RU2397024C1 - Method for production of nanosize metal powder - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention refers to the sphere of production of nanosize powder materials. Method for production of nanosize metal powder consists in grinding of hardly-deformed material with amorphous structure in high-speed disintegrator due to relative motion of impact elements with regulated speed and frequency of impacts. Previously material is selected with initial size of particles of not more than 80 micrometre, is thermally treated to form nanocrystalline inclusions in amorphous matrix. Grinding takes place at speed of impact element relative motion equal to 410-450 m/s and frequency of impacts 5000-8000 impact/s.

EFFECT: production of finer powder.

3 cl

Description

The invention relates to the field of creating nanosized powder materials by grinding, mixing and mechanical activation of metal amorphous and microcrystalline compositions and can be used in the chemical industry (catalysts, adsorbents for water purification), powder metallurgy (activators of sintering powders), production of cermet, soldering and welding and other areas.

Among modern grinding devices, the most suitable for producing nanosized metal powders, from the point of view of achieving a high degree of grinding on them, the intensity of machining (activation) and productivity, are disintegrators, centrifugal and jet mills. In these devices, a free-kick mode is implemented (collision speeds in them can reach 450 m / s).

Known methods of grinding materials (1. RU No. 93007674 A, class B02C 19/00, 1995; 2. RU No. 2211090, class B02C 13/22, 2002; 3. SU No. 1766514 A2, class B02C 19/00, 1992), where in order to increase the grinding efficiency, fineness of grinding, various grinding plants and technologies are used. In them, the possibility of transferring mechanical energy to the processed substance largely depends on the design of the installation (disintegrator, mill), as well as grinding conditions: on the speeds of the shock elements, the frequency of collisions of the particles of the processed material. A disadvantage of the known methods is the inability to disperse the particles of the crushed material to the required speed and to provide the required path length and, accordingly, the kinetic energy of the processed particles by controlling the frequency of collisions. These factors ultimately determine the possibility of obtaining a nanoscale powder of the required fraction (3-100) nm.

The closest in technical essence and the achieved effect is a method for producing a metal powder of an amorphous structure according to patent SU No. 1560321 A1 (class B02C 19/00, dated 10.12.87). The method for producing the powder consists of a two-stage grinding of the material with an amorphous structure in a high-speed disintegrator due to the relative movement of the shock elements. Hardly deformed metal material is first crushed at a speed of relative movement of the shock elements of 50-130 m / s and a shock frequency of 400-600 beats / s to a particle size of 1-3 mm. Then the crushing product is crushed to the desired fraction (100 μm or less) at speeds of relative movement of the shock elements 250-400 m / s and a frequency of 10000-30000 beats / s. A metal powder of an amorphous structure of a fraction of 2-100 μm is obtained.

The disadvantage of this method is the inability to obtain a finer powder, including the desired fraction (3-100) nm. Under the grinding conditions specified in the method (the speeds of the relative motion of the shock elements and the frequency of collisions), it is possible to obtain a minimum particle size of an amorphous powder of only a fraction of 2-10 microns.

The technical result of the present invention is a method for producing a nanoscale metal powder fraction (3-100) nm from a hardly deformable material.

It was experimentally established that the technical result is achieved by grinding, under certain conditions, a material with an amorphous structure in a high-speed disintegrator, which can significantly increase the kinetic energy of the impacted particles of the processed powder, at relative speeds of the shock elements 410-450 m / s and impact frequency 5000-8000 beats ./from.

In addition, the initial particle size of the selected processed (crushed) amorphous powder should not exceed 80 microns. The structure of such particles should have 30-50% by volume of nanocrystalline inclusions, which, being in the amorphous matrix, are stress concentrators, and disintegration of the powder material occurs over these zones.

The formation of nanocrystalline inclusions in the required quantities is carried out due to preliminary heat treatment (crystallization annealing) of the crushed amorphous material at temperatures (0.4-0.6) T of liquidus for at least one hour.

Variations in the parameters of the processing mode of the material (the speed of the relative motion of the shock elements and the frequency of collisions) both towards their decrease and towards their increase lead to the impossibility of obtaining nanosized powders of the required fraction.

With a decrease in the speed of the relative motion of the shock elements less than 410 m / s and an increase in the frequency of impacts over 8000 beats / s, the minimum fraction of the processed material is 2 μm. With an increase in the relative velocity of the impact elements of more than 450 m / s and a decrease in the frequency of impacts of less than 5000 beats / s, an intensive conglomeration of the resulting particles is observed, which can lead to failure of the rotor system of the disintegrator (sintering and sticking of the processed material to the fingers and rotor of the disintegrator) .

Only the fulfillment of these conditions in the proposed method provides for the production of nanosized metal powder fractions (from 3 to 100 nm) from hard-deformed magnetic, wear-resistant, vibration-damping materials and alloys-solders, etc. The obtained nanosized metal powder has unique properties (physical, chemical, mechanical) of nanomaterials .

Example 1. To obtain a nanoscale powder of the fraction (50-100) nm, an amorphous powder of the AMAG-200 grade based on iron (Fe-Cu-Nb-Si-B system) of a fraction of 60-80 μm was selected.

Pre-amorphous powder is heat treated (crystallization annealing) in a vacuum electric furnace of the type SNVE-1.3.1 / 16 I4 at a temperature (0.4-0.6) T of liquidus for 1 hour to form nanocrystalline inclusions. According to the results of X-ray diffraction analysis, the particles of the annealed powder of the AMAG-200 brand contain a crystalline phase in the form of nanoscale inclusions of 30% by volume.

Next, the heat-treated powder is subjected to single-stage grinding in a high-speed disintegrator type DESI-11. To prevent the oxidation of chemically active substances, grinding can be carried out in an argon atmosphere.

The powder is fed through a metering device to the working area of the disintegrator and the material is processed at a rotor speed of 410 m / s and a frequency of 5000 beats / s. The frequency of the impact is determined by calculation, based on the speed of rotation of the rotors, the number of shock elements (fingers of the rotor) and the dosed flow of material into the working area of the disintegrator. The obtained nanosized powder, passing through the discharge channel and the cyclone, is collected in a special vacuum receiving container of the disintegrator, which has a liquid system that excludes the pyrophoricity of the powder.

Example 2. To obtain a nanoscale powder of a fraction (3-5) nm, a powder is selected from an amorphous and microcrystalline alloy (AMC) of the STEMET-1201 grade based on titanium (Ti-Cu-Zr-Ni system) of a fraction of 50-80 μm.

Pre-amorphous STEMET-1201 powder is heat treated (crystallization annealing) in a vacuum electric furnace of the SNVE-1.3.1 / 16 I4 type at a temperature (0.4-0.6) T of liquidus for 1 hour. An x-ray diffraction analysis of the annealed amorphous powder is carried out, which shows the presence of crystalline phases in the form of nanoscale inclusions of 50% by volume.

After that, the heat-treated powder is subjected to single-stage grinding in a high-speed DESI-11 disintegrator. To prevent the oxidation of chemically active substances, grinding can be carried out in an argon atmosphere.

The crushed powder is fed through a metering device to the working area of the disintegrator and the material is processed at a rotor speed of 450 m / s and a frequency of 8000 beats / s, which is determined by calculation for each disintegrated material, based on the speed of rotation of the rotors, the number of shock elements and the dosed input material into the working area of the disintegrator. The obtained nanosized powder of the fraction (3-5) nm, passing the discharge channel and the cyclone, is collected in a special evacuated receiving container of the disintegrator, which has a liquid system that excludes pyrophoricity.

The phase composition of the obtained nanosized powders (examples 1 and 2) was determined by X-ray diffraction analysis on a DRON-4M type X-ray diffractometer (or a "Bruker" type diffractometer). The microstructure was studied and the geometric characteristics of the powder particles were determined by scanning electron microscopy (SEM) using a Camscan-4DV scanning electron microscope.

Thus, the studies showed that, subject to the selected grinding conditions, it was possible to obtain a metal powder of a given fractional composition having a nanocrystalline structure by single-stage grinding of a heat-treated powder with an amorphous structure in a disintegrator. This allows us to develop a new generation of special-purpose equipment by powder metallurgy using nanosized metal powders (soft magnetic, corrosion and erosion-resistant, high-strength, etc.).

Claims (3)

1. A method of producing a nanosized metal powder by grinding a hard-to-deformable material with an amorphous structure in a high-speed disintegrator due to the relative movement of the shock elements with a regulated speed and frequency of impacts, characterized in that the material with the initial particle size of not more than 80 μm is preliminarily selected, subjected to heat treatment, in which nanocrystalline inclusions are formed in an amorphous matrix, and then crushed at the speeds of relative motion of the shock element ov 410-450 m / s and impact frequency 5000-8000 bpm. 2. The method according to claim 1, characterized in that the nanocrystalline inclusions are obtained by preliminary heat treatment of the amorphous material at temperatures (0.4-0.6) T of liquidus for at least one hour. 3. The method according to claim 1, characterized in that the nanocrystalline inclusions located in the amorphous matrix comprise 30-50% by volume.