RU2569875C1 - Method of production of material containing lanthanum hexaboride and titanium diboride - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: cylindrical blank is pressed out of mechanically activated mixture of powders of titanium oxide TiO₂, lanthanum oxide La₂O₃ and boron, the produced cylindrical blank is heated in vacuum chamber at temperature 300-350°C, and by tungsten coil the burning reaction is initiated under mode of self-spreading high temperature synthesis.

EFFECT: production of qualitative material containing TiB₂ and LaB₆.

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Description

The invention relates to the field of powder metallurgy, in particular to the production of materials containing lanthanum hexaboride and titanium diboride, by the method of self-propagating high temperature synthesis (SHS) and mechanical activation, can be used to obtain materials for the cathode industry.

A known method of producing lanthanum hexaboride (RU 2477340, publ. 03/10/2013), which relates to electrolytic methods for producing pure lanthanum hexaboride.

The method is carried out by the joint electrowinning of lanthanum and boron from a chloride melt at the cathode and their subsequent interaction at the atomic level. The process is carried out in a three-electrode quartz cell, where a tungsten rod serves as a cathode, a glass-carbon rod sealed in pyrex serves as a reference electrode, and a glass-carbon crucible is used as an anode and at the same time as a container. The ultrafine powder of lanthanum hexaboride is synthesized by potentiostatic electrolysis from an equimolar KCl-NaCl melt containing lanthanum trichloride and potassium fluoroborate in an atmosphere of purified and dried argon at potentials from -2.0 to -2.6 V relative to a glassy carbon reference electrode at a temperature of 700 ± 10 ° C.

The technical result is: obtaining a pure target product due to the good solubility of the background electrolyte in water, as well as reducing energy costs. However, this method of obtaining lanthanum hexaboride is quite long, and its technological support is quite difficult on an industrial scale.

A known method of producing lanthanum hexaboride (G.V. Samsonov. Borides. Atomizdat, 1975). This is a plasma-chemical method, the high temperature and concentration of the substance in the plasma jet determine the almost instantaneous reaction and the high purity of the final product. However, the widespread use of this method in industry is constrained by the instability of large plasma flows and high energy costs.

Closest to the technical nature of the claimed invention is a method for producing lanthanum hexaboride by sintering (G.V. Samsonov. Borides. Atomizdat, 1975). This method of manufacturing cathodes from lanthanum hexaboride includes: cold pressing followed by sintering with the addition of an activating additive to improve sintering conditions. However, the sintering temperature is quite high (T = 2000 ° C and above) and the sintering time is long, as a result of which large energy inputs are required. In addition, compounds formed as a result of the interaction of the metal and the additive degrade the mechanical properties of the cathode.

The task is to obtain high-quality material by a method that ensures a reduction in energy costs, an increase in productivity.

The proposed method for producing titanium diboride TiB ₂ and lanthanum hexaboride LaB ₆ material is that a cylindrical blank is pressed from a mechanically activated mixture of powders of titanium oxide TiO ₂ , lanthanum oxide La ₂ O ₃ and boron in the following ratio of components, wt. %:

TiO ₂ 5-10 La ₂ o ₃ 20-30 AT 60-70

The resulting cylindrical billet is heated in a vacuum chamber at a temperature of 300-350 ° C. Then they initiate a combustion reaction in it with a tungsten spiral in the regime of self-propagating high-temperature synthesis.

The method of obtaining containing titanium diboride TiB ₂ and lanthanum hexaboride LaB ₆ material is as follows. The starting powders of titanium oxide TiO ₂ , lanthanum oxide La ₂ O ₃ and boron B are mixed in the ratio, wt. %: TiO ₂ 5-10, La ₂ O ₃ 20-30, B 60-70. The resulting mixture of powders is mechanically activated, pressed into a blank in the form of tablets with a diameter of 30 mm, a height of 20 ± 2 mm and a density of 2500-3000 kg / m ³ . The resulting preform is preheated in a vacuum chamber at 300-350 ° C, which allows to increase its thermodynamic characteristics. Without heating or with weak heating of the initial preform (less than 300 ° C), the synthesis of reagents is not carried out completely, intermediate phases remain, which adversely affects the target material. After preliminary heating of the sample, a combustion reaction in the SHS mode in a vacuum chamber is initiated by a tungsten spiral. The result is samples in the form of tablets with a diameter of 30 ± 1 mm and a height of 20 ± 4 mm.

Example 1

The initial powders of chemical purity of titanium oxide TiO ₂ , lanthanum oxide La ₂ O ₃ and boron B are mixed in the ratio, wt. %: 10:20:70, mechanically activated in an AGO-2 ball-type planetary mill for 10 minutes with a frequency of 15 Hz, a workpiece with a diameter of 30 mm, a height of 20 mm and a density of 3000 kg / m ^{3 was} pressed, heated to 300 in a vacuum chamber ° C. Next, a reaction in the SHS mode is initiated by a tungsten helix. As a result, the combustion wave passes unevenly. According to the results of x-ray phase analysis, there is the presence of unreacted titanium oxide TiO ₂ .

Example 2

The initial powders of chemical purity of titanium oxide TiO ₂ , lanthanum oxide La ₂ O ₃ and boron B are mixed in the ratio, wt. %: 10:30:60, mechanically activated in an AGO-2 ball-type planetary mill for 10 minutes with a frequency of 15 Hz, a workpiece with a diameter of 30 mm, a height of 20 mm and a density of 3000 kg / m ^{3 was} pressed, heated to 300 in a vacuum chamber ° C. Next, a reaction in the SHS mode is initiated by a tungsten helix. As a result, the combustion wave passes unevenly. According to the results of x-ray phase analysis, there is the presence of unreacted titanium oxide TiO ₂ and lanthanum oxide La ₂ O ₃ .

Example 3

The initial powders of chemical purity of titanium oxide TiO ₂ , lanthanum oxide La ₂ O ₃ and boron B are mixed in the ratio, wt. %: 5:25:70, mechanically activated in an AGO-2 ball-type planetary mill for 10 minutes with a frequency of 15 Hz, a workpiece with a diameter of 30 mm, a height of 20 mm and a density of 3000 kg / m ^{3 was} pressed, heated to 300 in a vacuum chamber ° C. Next, a reaction in the SHS mode is initiated by a tungsten helix. As a result, the combustion wave passes evenly. According to the results of x-ray phase analysis, the sample consists of titanium diboride TiB ₂ and lanthanum hexaboride LaB ₆ .

Example 4

The initial powders of chemical purity of titanium oxide TiO ₂ , lanthanum oxide La ₂ O ₃ and boron B are mixed in the ratio, wt. %: 5:25:70, mechanically activated in an AGO-2 ball-type planetary mill for 10 minutes with a frequency of 15 Hz, a workpiece with a diameter of 30 mm, a height of 20 mm and a density of 3000 kg / m ^{3 was} pressed, heated to 150 in a vacuum chamber ° C. Next, a reaction in the SHS mode is initiated by a tungsten helix. As a result, the combustion wave passes unevenly and not over the entire volume of the sample. According to the results of x-ray phase analysis, there is the presence of unreacted titanium oxide TiO ₂ , as well as the presence of transition phases of lanthanum borate LaBO ₃ .

Example 5

The initial powders of chemical purity of titanium oxide TiO ₂ , lanthanum oxide La ₂ O ₃ and boron B are mixed in the ratio, wt. %: 5:25:70, without mechanical activation, a workpiece is pressed with a diameter of 30 mm, a height of 20 mm and a density of 3000 kg / m ³ , heated in a vacuum chamber to 300 ° C. Next, a reaction in the SHS mode is initiated by a tungsten helix. As a result, the combustion wave passes unevenly and not over the entire volume of the sample. According to the results of x-ray phase analysis, there is the presence of unreacted titanium oxide TiO ₂ and lanthanum oxide La ₂ O ₃ , as well as the presence of transition phases of lanthanum borate La ₂ BO ₃ .

Example 6

The initial powders of chemical purity of titanium oxide TiO ₂ , lanthanum oxide La ₂ O ₃ and boron B are mixed in the ratio, wt. %: 5:25:70, mechanically activated in an AGO-2 ball-type planetary mill for 10 minutes with a frequency of 15 Hz, a workpiece with a diameter of 30 mm, a height of 20 mm and a density of 3000 kg / m ^{3 was} pressed, heated to 300 in a vacuum chamber ° C. Next, a reaction in the SHS mode is initiated by a tungsten helix. Thermomechanical destruction of the sample occurs. As a result, the combustion wave passes unevenly and not throughout the volume. According to the results of x-ray phase analysis, there is the presence of unreacted titanium oxide TiO ₂ and lanthanum oxide La ₂ O ₃ .

According to the results of x-ray phase analysis, it was found that the resulting material contains TiB ₂ , LaB ₆ .

Thus, the proposed combination of features of the invention allows to obtain materials containing lanthanum hexaboride and titanium diboride, of high quality with reduced energy consumption. This proves the result of x-ray phase analysis. The resulting materials can be used as electrodes for plants for various purposes.

Claims (1)

A method of obtaining a material containing titanium diboride TiB ₂ and lanthanum hexaboride LaB ₆ material, characterized in that a cylindrical workpiece is pressed from a mechanically activated mixture of powders of titanium oxide TiO ₂ , lanthanum oxide La ₂ O ₃ and boron in the following ratio of components, wt. %:
TiO ₂ 5-10 La ₂ o ₃ 20-30 AT 60-70
The obtained cylindrical billet is heated in a vacuum chamber at a temperature of 300-350 ° C and a combustion reaction is initiated by a tungsten spiral in it in the mode of self-propagating high-temperature synthesis.