RU2534181C2 - Production of electrolytic metal powders - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to powder metallurgy, particularly, to materials intended for production of electrolytic metal powders. It can be used in production of catalysts, electroplating and electronics. Cathodic reduction of metal ions from metal salt solution is carried out in electrolytic cell with rotary cathode and anode or insoluble anode. Cathode is composed of a rod with partially (90-99%) isolated surface. Cathodic reduction is executed at current density from 100 A/dm² to origination of electrolyte plasma and metal salt concentration over 100 g/l to saturation.

EFFECT: higher process efficiency at high yield and quality of powder.

3 ex

Description

The invention relates to powder metallurgy, to methods for producing electrolytic metal powders and may find application in the manufacture of catalysts, powder metallurgy, electroplating, electronics.

The known method (RF Patent No. 2420613, C25C 5/02, 2010), where the powder is obtained by electrolysis of an aqueous solution of a metal salt with a concentration of 30-70 g / l at a current density of 20-40 A / DM ² .

The low productivity of this method is limited by a low current density (20-40 A / dm ² ) and a low concentration of metal salt (30-70 g / l).

The known method (RF Patent No. 2469111, C22B 7/00, 2012), taken as a prototype, in which the production of copper powders is carried out by electrolysis of a solution containing 20-30 g / l [Cu (NH ₃ ) ₄ ] Cl ₂ and 50 g / l NaC1, at a current density of 20-50 A / DM ² .

The disadvantage of this method is the lack of productivity of 0.14 kg / (A · m ² · h) of copper powder. The reason for the insufficient productivity is a low current density (20-50 A / dm ² ) and a low concentration of metal salt (20-30 g / l).

The technical task of the proposed method is to increase the productivity of the process of producing electrolytic metal powders by increasing the current density from 100 A / dm ² and above until the appearance of electrolyte plasma and increasing the concentration of metal salt up to saturation.

The solution to the technical problem is achieved by the fact that in the method for producing electrolytic metal powders, including cathodic reduction of metal ions from an aqueous solution of a metal salt in an electrolyzer with a rotating cathode and with an anode of the corresponding metal or with an insoluble anode, the process is carried out using a cathode made in the form of a rod with partially (90-99%) of an insulated surface, with a current density of 100 A / dm ² and above until the appearance of electrolyte plasma, and a metal salt concentration of more than 100 g / l until saturation.

The increase in productivity is provided by an increase in the rate of electrochemical reaction. In this case, the cathode as a whole, made in the form of a copper rod, provides current supply and heat removal from the working parts of the surface, which inevitably is released when significant currents flow. The rotation of the cathode provides separation of the resulting metal powder from the surface of the cathode, that is, preventing an increase in the surface of the cathode and a decrease in current density.

The application of the invention is illustrated by the following examples.

Example No. 1

In an electrolyzer with a capacity of 2 liters, filled with a saturated solution of copper sulfate, an anode of sheet copper with an area of 1 dm ^{2 is} placed. The cathode is made in the form of a copper rod with a diameter of 8 mm and a length of 100 mm, a part of the cathode surface (95%) is coated with dielectric galvanic-resistant varnish, leaving 30 uninsulated sections of 0.5 mm ² with a total area of 15 mm ² . The cathode is mounted at a distance of 10 mm from the anode and rotated at a speed of 500 rpm. A voltage of 20 V is supplied to the electrolyzer from a DC power source. After passing a current of 6 A (current density 4000 A / dm ² ) for 1 hour, the resulting copper powder is removed from the electrolyzer and washed in distilled water, and then in acetone and dried. The mass of the obtained powder is 6.9 g. The current efficiency is 96%. Thus, the performance of the process for producing copper powder by the proposed method is 76 kg / (A · m ² · h). The resulting powder is sieved through a sieve with a cell of 71 μm. The bulk density of the powder is 0.9 g / ml. The electrical conductivity of the powder, with a slight compaction of it in the measuring cell, is 2.5 Ohms. See. The properties of the obtained powder indicate its high quality.

Example No. 2

In the electrolyzer filled with 2 liters of electrolyte containing 350 g / l of nickel sulfate and 50 g / l of ammonium chloride, an anode of nickel foil with an area of 2 dm ^{2 is} placed. The cathode is made of a rod with a diameter of 10 mm with a threaded thread in increments of 1 mm. The core is coated with epoxy. After curing the epoxy resin, the cathode surface is ground until a thread crest appears. As a result, an uninsulated spiral line 0.2 mm wide is obtained on the cathode surface. The working surface area is 300 mm ² . The cathode is lowered into the cell at a distance of 20 mm from the anode to a depth of 50 mm and rotated at a speed of 750 rpm A current of 3 A is passed through the electrolyzer for one hour. 3.1 g of nickel powder are obtained with a current efficiency of 94%. The current density in this case is 100 A / dm ² .

Example No. 3

The cathode is made according to example 2 and additionally along the axis of the rod on the surface make grooves in increments of 1 mm. On the surface of the rod are formed protrusions of a pyramidal shape. Further, as in example 2, isolate and grind the surface to obtain uninsulated peaks of the protrusions. The total area of the working non-insulated part of the cathode is 10 mm ² . The cathode is rotated in an electrolyzer filled with a solution of copper sulfate with a concentration of 100 g / l at a speed of 1000 rpm. A current of 10 A is passed through the electrolyzer for 1 hour. The current density is 10,000 A / dm ² . The resulting copper powder weighing 10.5 g, with a current efficiency of 87%, is sieved through a sieve with a mesh size of 50 μm. The bulk density of the powder is 0.65 g / ml, the electrical resistivity is 2.5 Ohm · cm. The productivity of the process is 91.4 kg / (A · m ² · h).

As follows from the examples, the proposed method for producing electrolytic metal powders can significantly (500-600 times) increase the productivity of the process with a high current output and high quality powder.

In addition, the invention allows to reduce the cost of production of metal powders by reducing energy consumption, reducing the metal consumption of equipment and simplifying the technology. There are additional possibilities for regulating the process and the properties of the obtained powders due to the expansion of technological modes.

Claims (1)

A method for producing an electrolytic metal powder, including cathodic reduction of metal ions from an aqueous solution of a metal salt in an electrolyzer with a rotating cathode made in the form of a rod with a partially (90-99%) insulated surface and an anode of the corresponding metal or insoluble anode at a current density of 100 A / dm ² and above until the occurrence of electrolytic plasma and a metal salt concentration of more than 100 g / l until saturation.