RU2539523C1 - Electrolytic method of obtaining nanosized cerium disilicide powder - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to obtaining nanopowders of cerium disilicide and can be used for manufacturing current-conducting and resistive elements of integrated circuit. Method of electrolytic obtaining nanosized cerium disilicide powder includes synthesis of cerium disilicide from melted media in atmosphere of purified and dried argon. Synthesis is carried out from halogenide melt. As cerium source used is water-free cerium chloride, as silicon source - sodium fluorosilicate, and as solvent - equimolar mixture of potassium and sodium chlorides with the following component ratio, wt %: cerium chloride 1.0-5.0, sodium fluorosilicate 1.0-4.0, the remaining part - equimolar mixture of potassium and sodium chlorides. Process is carried out at temperature 700°C, current density 0.2 A/cm² and electrolysis potentials relative to glass-carbon comparison electrode from -2.2 to -2.6. Target product is obtained in pure form due to good solubility of equimolar melt of potassium chloride and sodium chloride in water and solubility of formed cerium fluoride with potassium fluoride.

EFFECT: increased rate of target product synthesis from melted electrolyte.

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Description

The invention relates to the production of cerium disilicide nanopowders and can be used to obtain functional ceramics with a number of unique properties necessary for the manufacture of conductive and resistive elements of integrated circuits.

A known method of producing crystalline niobium silicide. The initial silicon powders of 40-400 microns and niobium less than 63 microns are taken in the ratio of 1.33-1.38: 1 to obtain a single-phase product and 1.44-1.69: 1 to obtain a multiphase product. Carry out mechanical activation in an inert environment for 0.5-2 minutes. The ratio of the mass of the powder to the mass of the balls is 1:20. The resulting powder is pressed and locally heated in an argon atmosphere, initiating an exothermic reaction of the formation of niobium silicide in the mode of self-sustaining combustion. The technical result is to obtain a single-phase crystalline niobium silicide.

Known methods for producing silicides of rare earth metals [G.V. Samsonov Chemistry of rare-earth metal silicides. Advances in Chemistry, 1982, T.XXXI, Issue 12, p. 1478-1495]: a) direct connection of rare-earth metals with silicon [R. Vogel, Ztschr. anorg. Chem., 61, 46 (1909)]; b) reduction of rare earth metal oxides with silicon [B.C. Neshpor, G.V. Samsonov, ZhPKh, 33, 993 (1960)]; c) electrolysis of molten media containing rare earth metals and silicon [M. Dodero, C.r., 199, 566 (1934); Bull. Soc. Chim. France, 17, 545 (1950)].

The closest is the high-temperature electrochemical synthesis from molten media containing rare earth metals and silicon.

The disadvantage of the above method is the high temperature of synthesis and contamination by-products, in particular silicates, as well as the inability to obtain an individual phase of disilicide.

The objective of the present invention is to obtain a nanosized powder of cerium disilicide, increasing the rate of synthesis of the target product from the molten electrolyte.

The essence of the invention lies in the fact that they carry out the joint electrowinning of cerium and silicon from a halide melt at the cathode and their subsequent interaction at the atomic level with the formation of nanosized cerium disilicide powders. The process is carried out in a three-electrode quartz cell, where a tungsten rod serves as a cathode; anode and at the same time a container - a glassy carbon crucible; reference electrode - glassy carbon rod. The synthesis of cerium disilicide is carried out by potentiostatic electrolysis from an equimolar melt KCl-NaCl containing cerium trichloride and sodium fluorosilicate in an atmosphere of purified and dried argon. Anhydrous cerium trichloride is used as a cerium source, sodium fluorosilicate as a silicon source, and an equimolar mixture of potassium and sodium chlorides as a solvent in the following ratio of components, wt.%:

cerium chloride 1.0 ÷ 5.0;

sodium fluorosilicate 1.0 ÷ 4.0;

the rest: an equimolar mixture of potassium and sodium chlorides.

Potentiostatic electrolysis is carried out on a tungsten cathode at potentials from -2.2 to -2.6 V relative to the glassy carbon reference electrode at a temperature of 700 ° C. The optimal duration of the electrolysis process is 60 ÷ 90 minutes The resulting cathode-salt pear, consisting of cerium disilicide, is washed from cerium fluoride with potassium fluoride.

The components of the electrolytic bath were selected on the basis of thermodynamic analysis and kinetic measurements of the combined electrowinning of cerium and silicon from halide melts. Of the oxygen-free cerium and silicon compounds, cerium chloride and sodium fluorosilicate are fairly low melting and highly soluble in the equimolar KCl-NaCl melt. The solvent (equimolar KCl-NaCl melt) is selected from the following considerations: the decomposition voltage of the molten KCl-NaCl mixture is greater than that for CeCl ₃ and Na ₂ SiF ₆ melts; good solubility in water.

The phase composition was identified by X-ray diffraction analysis on a DRON-6 diffractometer, which showed the presence of only the CeSi ₂ phase. The images in figures 1, 3, 5 correspond to examples 1, 2, 3.

Figure 1 - X-ray powder powder of cerium disilicide CeSi ₂ (line 1) obtained from a melt KCl-NaCl on a tungsten cathode at φ = -2.2 B.

Figure 3 - X-ray powder powder of cerium disilicide CeSi ₂ (line 1) obtained from a melt KCl-NaCl on a tungsten electrode at φ = -2.5 B.

Figure 5 - X-ray powder powder of cerium disilicide CeSi ₂ (line 1) obtained on a tungsten cathode at φ = -2.6 B.

Particle size was determined by a Fritsch Analysette-22 laser diffraction analyzer. The images in figures 2, 4, 6 correspond to examples 1, 2, 3.

Figure 2 is a diagram of the size distribution of particles obtained at 700 ° C by electrochemical synthesis at i = 0.2 A / cm ² .

Figure 4 - Diagram of the size distribution of particles obtained at 700 ° C by electrochemical synthesis at i = 0.2 A / cm ² .

6 is a diagram of the size distribution of particles obtained at 700 ° C by electrochemical synthesis at i = 0.2 A / cm ² .

Example 1

A salt mixture weighing 32.66 g containing 1.53 g CeCl ₃ (4.70 wt.%) Is placed in a 40 ml glass-carbon crucible; 1.13 g of Na ₂ SiF ₆ (3.46 wt.%); 16.8 g of KCl (51.44 wt.%); 13.2 g of NaCl (40.42 wt.%). The crucible with the salt mixture is placed in a quartz cell and kept in a dry argon atmosphere until the system melts. Upon reaching a working temperature of 700 ° C, a tungsten cathode is lowered into the melt, electrolysis is carried out at a potential of -2.2 V relative to the glassy carbon reference electrode (current density 0.2 A / cm ² ). The cathode-salt pear, consisting of cerium disilicide, is washed from cerium fluoride with potassium fluoride. The particle size of the obtained cerium disilicide powder is up to 100 nm.

Example 2

In a 40 ml glassy carbon crucible, a salt mixture weighing 34.09 g containing 1.53 g CeCl ₃ (4.49 wt%) is placed; 2.56 g of Na ₂ SiF ₆ (7.51 wt.%); 16.8 g of KCl (49.30 wt.%); 13.2 g of NaCl (38.72 wt.%). The crucible with the salt mixture is placed in a quartz cell and kept in a dry argon atmosphere until the system melts. Upon reaching a working temperature of 700 ° C, a tungsten cathode is lowered into the melt, electrolysis is carried out at a potential of -2.5 V relative to the glassy carbon reference electrode (current density 0.2 A / cm ² ). The cathode-salt pear, consisting of cerium disilicide, is washed from cerium fluoride with potassium fluoride. The particle size of the obtained cerium disilicide powder is up to 100 nm.

Example 3

A salt mixture weighing 42.83 g containing 1.53 g CeCl ₃ (3.60 wt.%) Is placed in a 40 ml glass-carbon crucible; 11.30 g of Na ₂ SiF ₆ (7.72 wt.%); 16.8 g of KCl (49.79 wt.%); 13.2 g of NaCl (26.39 wt.%). The crucible with the salt mixture is placed in a quartz cell and kept in a dry argon atmosphere until the system melts. Upon reaching a working temperature of 700 ° C, a tungsten cathode is lowered into the melt, electrolysis is carried out at a potential of -2.6 V relative to the glassy carbon reference electrode (current density 0.2 A / cm ² ). The cathode-salt pear, consisting of cerium disilicide, is washed from cerium fluoride with potassium fluoride. The particle size of the obtained cerium disilicide powder is up to 100 nm.

The technical result is:

- obtaining nanosized particles of cerium disilicide;

- obtaining the target product in pure form due to the good solubility of the equimolar melt of potassium chloride and sodium chloride in water, the solubility of the resulting cerium fluoride with potassium fluoride.

Claims (1)

The method of electrolytic production of nanosized cerium disilicide powder, including the synthesis of cerium disilicide from molten media in an atmosphere of purified and dried argon, characterized in that the synthesis is carried out from a halide melt, anhydrous cerium chloride is used as a source of cerium, sodium fluorosilicate is used as a source of silicon, and as a solvent, an equimolar mixture of potassium and sodium chlorides in the following ratio of components, wt.%:
cerium chloride 1.0 ÷ 5.0;
sodium fluorosilicate 1.0 ÷ 4.0;
the rest: an equimolar mixture of potassium and sodium chlorides,
the process is carried out at a temperature of 700 ° C, a current density of 0.2 A / cm ² and electrolysis potentials relative to the glassy carbon reference electrode from -2.2 to -2.6 B.

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