RU2846622C2 - Apparatus for producing powder with core-shell structure - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to powder metallurgy, particularly, to production of powder with core-shell structure. Plant for producing powder with a core-cladding structure comprises a core material powder dispenser, connected by a pipe to a plasmatron comprising an annular nozzle, made in the form of a thin-walled funnel, and a cooler of the obtained powder. Proportioner of core material powder contains bunker connected with dosing disk made with possibility of rotation at constant speed and movement of core material powder in zone of outlet nozzle. Plasmatron additionally comprises igniter electrode with nozzle and guide sleeve for supply of precursor of shell material from feed drum.

EFFECT: higher quality of produced powders.

1 cl, 1 dwg

Description

Field of technology to which the invention relates

The invention relates to methods for producing powder materials with a core-shell structure using plasma technology.

State of the art

The closest to the claimed technical solution in terms of the set of essential features, adopted as a prototype, is a known installation for producing powder with a core-shell structure (CN111872378, publication date 03.11.2020), containing a core material powder dispenser connected by a pipeline to a plasma torch containing an annular nozzle made in the form of a thin-walled funnel, and a cooler for the resulting powder. The disadvantage of this known installation is the need for high-precision balancing of the precursor, since at a high frequency of its rotation around the axis using the first drive mechanism, with a significant imbalance, large centrifugal forces and vibrations will arise, which will negatively affect the process of dispersion of droplets of the precursor material. High-quality coating of the core of a powder particle of a given thickness with a drop of molten precursor during mechanical dispersion of the melt from the end surface of the precursor requires a highly accurate setting of the rotation frequency of the first drive mechanism, which can only be determined experimentally, which is also a disadvantage of the known method. A disadvantage of the prototype is also the liquid droplet deposition of the precursor material melt on the surface of the core powder particle, since the uniformity of the coating application will be significantly affected by the gravity of the drop and its partial flow to one side of the core particle surface is possible during the deposition process.

The problem solved by the present invention consists in increasing the productivity of manufacturing powder materials with a core/shell structure and improving the quality of the manufactured powder particles using plasma technology.

The technical result is achieved in that the installation for producing powder with a core-shell structure contains a powder feeder hopper connected in a process line, connected to a dosing disk of a dosing unit having a drive and a nozzle, the dosing unit is connected by a pipeline to a plasma torch for feeding a gas-powder mixture of the initial core material; the said plasma torch contains an anode, an ignition electrode with a nozzle and a guide sleeve for feeding a precursor from a feed drum, the installation contains a cooler for the obtained material.

List of drawing figures

Fig. 1 shows a device for implementing the method.

Implementation of the invention

Core-shell particles are a new class of composite materials that feature a set of unique characteristics provided by the particle structure. Each granule is a sphere consisting of two dissimilar or multifunctional materials - a core and a shell.

Fig. 1 shows a device illustrating a simplified diagram of the implementation of the proposed method for producing powder materials with a core-shell structure using plasma technology, in which the following is indicated: 1 - powder feeder hopper, 2 - dosing disk of the dosing unit with a drive and a nozzle, 3 - adjustable drive for rotating the dosing disk; 4 - sealed body of the dosing unit; 5 - pipeline for feeding the gas-powder mixture of the initial core material; 6 - wire precursor, 7 - plasma torch anode; 8 - ignition electrode with a nozzle and a guide sleeve for the precursor; 9 - feed drum with a coil of wire precursor; 10 - drive rollers of the feed adjustable drive for moving the precursor; 11 - guide sleeve; 12 - cooler; 13 - particles of core material powder; 14 - particles of the powder of the obtained core-shell material; 15 - cooler manifold; 16 - cooler chamber, 17 - inert gas supply to cooler chamber 16; 18 - inert gas supply to sealed body of dispenser 4; 19 - inert gas supply to gap between precursor 6 and guide sleeve 11; 20 - flow of produced cooled particles.

The initial powder of the core 13 is loaded into the hopper of the gas-powder mixture dispenser 1 in a volume sufficient for operation over a long period of time (up to several hours). From the hopper 1 of the dispenser, the initial powder of the core flows by gravity onto the dosing disk 2, which rotates at a given adjustable constant speed and moves the powder into the zone of the outlet nozzle, where the flow 18 of the inert gas captures it from the disk 2 and carries it away along the pipeline 5 towards the plasma torch. The speed of rotation of the disk 2, adjusted by the rotation drive 3 with constant parameters of the window of the hopper 1 and the cross-section of the nozzle, determines the volume of powder entering the working zone of the plasma torch per unit of time.

An arc discharge is excited between the precursor 6 and the inner surface of the nozzle. The precursor 6, which functions as a cathode, is subjected to intensive spraying in the cathode spot, the precursor material vapors are carried away by the inert gas supplied together with the precursor and which is a plasma-forming gas flow. The plasmoid formed in this case melts and spheronizes the initial powder, which is constantly supplied in the form of a gas-powder mixture of core material granules and inert gas through an annular nozzle in the form of a thin-walled funnel 7, which has a slope toward the center, where the precursor 6 is located. The design of the nozzle parts assumes the possibility of changing the width and angle of inclination of the slit in the process of selecting the optimal values of the process parameters. By changing the width and angle of inclination of the slit, it is possible to change the speed of movement of the initial powder particles in the working area of the plasma torch and, consequently, the thickness of the shell without changing the flow rate of the transporting inert gas for different materials and sizes of the core and shell parts.

In front of the gap formed by the nozzle and the anode, a volume in the form of a ring is organized, the cross-section of which significantly exceeds the cross-section of the nozzle itself. In this volume, tangentially, through two holes located exactly opposite each other, a gas-powder mixture is introduced, which is fed from the feeder through the pipeline 5 and the channel in the plasma torch body. Due to the tangential arrangement of the holes, the gas-powder mixture makes a circular motion in the volume and is gradually sucked into the gap, forming a uniform and axially symmetric flow. Getting into the plasmoid, the particles of the original powder 5 are heated, partially or completely melted, acquiring a spherical shape due to the forces of surface tension, at the same time, vapors or particles of nanopowder of the precursor material 6 are deposited on their surface, forming a shell. The particles then leave the plasmoid region and are cooled in inert gas flows 17 supplied to the cooling chamber 16, crystallizing and forming granules of particles with a core-shell structure, which are directed to the collector 15 and then by flow 20, for example, for separation.

The proposed process does not require high intensity of evaporation of the precursor material with the simultaneous need to obtain high temperature, density and linear dimensions of the plasmoid, sufficient for the particles that have entered it to completely or partially melt and acquire a spherical shape. The magnitude of the electric discharge power required for this should not cause explosive evaporation of the precursor and especially its partial melting, which will interfere with the process, provided that the precursor is the only cathode in the electrode system.

The use of a dosing disk for feeding the initial core powder, the use of a precursor shell in the form of a wire, the use of an inert gas to prevent air from entering the plasma torch working area through the precursor feed channel and cooling the precursor, the application of a shell to the core in a controlled gas environment using the gas-dynamic dispersion of the melt, and additional spheronization of the initial powder particles in the plasma torch working chamber make it possible to increase the productivity of manufacturing powder materials with a core-shell structure and improve the quality of the manufactured powder particles using plasma technology.

Claims (1)

An installation for producing a powder with a core-shell structure, comprising a core material powder dispenser connected by a pipeline to a plasma torch containing an annular nozzle made in the form of a thin-walled funnel, and a cooler for the produced powder, characterized in that the core material powder dispenser comprises a hopper connected to a dosing disk made with the possibility of rotating at a constant speed and moving the core material powder into the area of the outlet nozzle, and the plasma torch additionally comprises an ignition electrode with a nozzle and a guide sleeve for feeding the shell material precursor from the feed drum.