RU2074267C1 - Method of preparing sphere-shaped nickel - Google Patents

Abstract

FIELD: electrolytic processes. SUBSTANCE: method includes precipitating nickel from sulfate-chloride solution onto conducting regions of dielectric- coated cathode basis, each region having the area not more than 0.5 sq.cm. Target regions are in the form of regular pyramids. In the beginning of precipitation, cathode current density reaches 0.6-0.8 A/sq.dm, maintained constant up to 0.25 of the total period, during the period of process within 0.25-0.5 of the total period current density is raised not more than by 0.01 A/sq. dm and then maintained constant up to 0.75 of the total period, and then raised by 1.5-3.0 A/sq.dm and maintained constant to the end of process. Precipitation area is cathode basis constituting one or several interconnected regular pyramids with conducting regions near their apexes, which is rotated with velocity 0.5-2 rpm. EFFECT: improved procedure. 2 cl, 3 dwg, 1 tbl

Description

 The invention relates to the electrolytic production of round-shaped nickel (in the form of separate disks, "rounds", etc.) by deposition on a cathode base. Nickel of this form is widely used as anodes during the process of nickel plating of metal parts.

 A known method of deposition of metal on small electrically conductive sections of the cathode base while passing an electric current through an electrolyte (patent US N 3860509, 1975). The plots are formed from the free ends of a plurality of thin electrical wires by placing them in a matrix of non-conductive material. The area of each plot is 0.0005-0.018 sq. Mm. The metal precipitate obtained on such a conductive surface, although it tends to radially expand at the beginning of the process, acquires a disk-shaped shape towards the end. In addition, the resulting metal deposit is very small due to its weak connection with the cathode base.

 A known method of producing "rounds" of electrolyte nickel 2.5 cm in size (Patent US N 4147597, 1979). Precipitation is carried out by passing a current through a sulfate-chloride electrolyte to circularly conducting electrically conductive sites isolated in the non-conductive surface of the cathode base. The surface of these areas is specially treated by grinding to obtain a clear "microfluid" with a size of 0.6-7.6 microns of a rounded or pyramidal shape. This makes it possible to reliably retain a cathode-based metal deposit during the metal deposition process. However, this method also does not allow to obtain nickel of the correct spherical shape.

 Closest to the proposed process is the deposition of spherical nickel by passing an electric current through a sulfate-chloride electrolyte using a durable cathode block containing a rigid plate of non-conductive material, inside of which there is a conductive metal assembly (US Pat. No. 4,082,641, 1978). The specified node is a series of metal rods that protrude above the stove, forming a network of flat electrically conductive sections, each of which has an area of 0.13-1.3 sq.cm. Deposition is carried out with a change in the density of the cathode current. During the time, which is half the entire deposition cycle, the initial cathode current density is increased by about three times, after which the rest of the deposition time is kept constant.

 This method allows to obtain a precipitate in the form of a crown of round or elliptical shape with a flat base. The total surface area of such a sediment is not less than three times the base area. However, the receipt of Nickel regular spherical shape using the present invention is impossible.

 The aim of the invention is to obtain electrolyte nickel of the correct spherical shape.

 This is achieved by the fact that in the method for producing spherical nickel, including its deposition from a sulfate-chloride electrolyte on electrically conductive sections of a cathode base coated with a dielectric, each of which has an area of not more than 0.5 cm2, when the cathode current density changes during deposition period t, deposition is carried out in areas having the shape of a regular pyramid, with an initial cathode current density of 0.6-0.8 A / sq. dm, which is then changed as follows (FIG. 1): from 0 to 1/4 t keep constant; from 1/4 t to 1/2 t increase by no more than 0.01 (A / sq. dm) / h; from 1/2 t to 1/4 t keep constant; at 3/4 t increase by 1.5-3 A / sq.dm; 3/4 t to t is kept constant.

Deposition on the top of the regular pyramid allows you to concentrate on it a stream of Ni ²⁺ cations, to avoid its dispersion over the surface, which happens when deposited on a flat substrate. Maintaining a current density of 0.6-0.8 A / sq. dm during the first quarter of the deposition period, in a conductive area with a small surface, it is possible to obtain a seed in the form of a dense ball. This is facilitated by the growth of metal along the planes of the regular pyramid. During the second quarter of the deposition period, the current density is increased by no more than 0.01 (A / sq. Dm) / h. This mode ensures uniform deposition of Nickel on the newly formed surface. However, some irregularities in the precipitate still form. They are smoothed over the next quarter of the period, keeping the current density constant. At the end of this part of the deposition period, there is some metal surface of regular spherical shape. To carry out further uniform deposition of nickel on this surface, the current density is increased by 1.5-3 A / sq. Dm, depending on the diameters of the balls that you want to obtain during the process. At the final stage, smoothing out small irregularities is carried out, bringing the surface of the sediment closer to the shape of the ball.

 An initial current density of less than 0.6 A / sq. Dm reduces the productivity of the process due to the slower growth of the ball surface. In addition, it is possible to distort the shape of the ball due to the growth of dendrites with an increase in the cathode current density by 1.5-3 A / sq. Dm at 3/4 t, and since the necessary surface does not have time to form. The growth of dendrites is also observed when establishing the initial current density of more than 0.8 A / sq.dm. Similarly, the distortion of the spherical shape of the deposited metal in case of excess current density over the claimed mode for 1 / 4t-1 / 2t is explained.

 If the current density at 3 / 4t is increased by less than 1/5 A / sq. Dm, then the productivity of the process decreases. The excess of current density over the upper limit, i.e. 3.5 A / sq. Dm, causes the growth of dendrites.

 In an embodiment of the method, the deposition is carried out on a cathode base, which is one or more interconnected regular pyramids coated with a dielectric, with electrically conductive areas near the vertices that rotate at a speed of 0.5-2 rpm.

 The vertices of the regular pyramids of such a cathode base in the electrolysis bath will be at different distances from the anodes between which it is placed. To achieve the goal of the claimed electrical modes, rotation of the base is used. If the rotation speed of the cathode base is less than 0.5 rpm or more than 2 rpm, the shape of the ball of the deposited metal is distorted. The simultaneous use of many cathode bases in the form of interconnected regular pyramids can increase the productivity of the process by increasing the number of deposition centers.

 The invention is illustrated in FIG. 1-3. The cathode for deposition of balls is shown in FIG. 2. Metal rods 1 are suspended on a common rod 2 with the possibility of rotation. On each such rod several cathode bases 3 are fixed, which are regular pyramids interconnected. The rods, rod and cathode bases are coated with a dielectric, highlighting the conductive areas with an area of not more than 0.5 square meters. see near the tops of the pyramids. Figure 3 separately shows the cathode base in the form of interconnected regular pyramids 4, covered with a dielectric 5, with electrically conductive sections 6.

 Obtaining nickel metal deposits of the correct spherical shape by electrolytic deposition on the electrically conductive sections of the cathode base, made in the form of a regular pyramid, under the claimed modes, is new and significantly different from the known analogues.

 Example 1. The method was used to obtain electrolyte nickel balls with a diameter of 2.5-3 cm.

 The cathode base was a titanium plate, on the surface of which titanium regular pyramids with a height of 30 mm were fixed in a checkerboard pattern on both sides. A dielectric coating was applied on both surfaces of the plate and the faces of the pyramids, highlighting the electrically conductive areas near the vertices of the pyramids with an area of 0.3 sq. Cm.

The cathode base was lowered into the electrolysis bath, secured to the cathode rod using conductive bars. Nickel anodes were placed on both sides of the cathode base, parallel to its plane. A solution containing was used as an electrolyte. g / l: NiSO ₄ x6 H ₂ O 250-330; NiCl ₂ x ₇ H ₂ O 71; H ₃ BO ₃ 18.

The temperature of the solution was 46-51 ^o C, pH 4.5. The total deposition time (period) is 8 days.

 The process was started at a cathode current density of 0.6 A / sq. Dm, which was maintained for 2 days. The next 2 days, the current density was increased at a rate of 0.01 (A / sq. Dm) / h, until it reached a value of 1.08 A / sq. Dm. After holding the cathode at a current density of 1.08 A / sq. Dm for 2 days, it was increased to 4.08 A / sq. Dm and was kept constant for 2 days as well.

 As a result, nickel of the correct spherical shape was obtained in the form of individual precipitates with a diameter of 2.5-2.8 cm. The resulting metal deposit was removed from the tops of the regular pyramids of the cathode base.

 Example 2. Obtaining balls of Nickel with a diameter of 3 cm was carried out on the cathode base in the form of connected regular pyramids, which were fixed on metal rods and hung on a common rod (see figure 2). Rods, rods and cathode bases were made of titanium. The titanium was covered with a dielectric, highlighting near the tops of the pyramids electrically conductive areas of 0.5 square cm. The composition of the electrolyte, its pH, temperature, and electrical conditions of the deposition process are shown in Example 1. Deposition was carried out on cathode substrates rotating around its axis at a speed of 1.5 rpm.

 As a result of the process, nickel balls with a diameter of 3.0-3.2 cm were obtained.

 Obtaining nickel balls of other diameters was carried out using the cathode bases described in examples 1 and 2, changing the duration of the deposition process or the number of deposition centers.

 The results of nickel deposition at different modes of the process are presented in table 1.

Claims (2)

1. A method for producing spherical nickel, including its deposition from a sulfate-chloride electrolyte on electrically conductive sections of a dielectric coated cathode base, each of which has an area of not more than 0.5 cm ² , when the cathode current density changes during the deposition period, characterized in that the deposition is carried out on the portions having the shape of a regular pyramid, wherein at the beginning of deposition adjusted cathode current density 0.6 0.8 a / dm ^2, and the current density to 1/4 of the period is kept constant, then tightly be current for 1/4 1/2 period is increased by not more than 0.01 A / dm ² • h, then within 1/2 3/4 period is maintained constant, then for 3/4 period is increased by one , 5 3 A / dm ² , after which they are kept constant for a period of time from 3/4 to the end of the deposition period. 2. The method according to claim 1, characterized in that the deposition is carried out on the cathode base, which is one or more interconnected regular pyramids, with electrically conductive sections near the peaks, which rotate at a speed of 0.5 to 2.0 min ^-1 .

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