RU2799512C2 - Method for obtaining nanoscale multioxides of refractory metals - Google Patents

Abstract

FIELD: chemical industry; aerospace and rocket technology.

SUBSTANCE: invention can be used in the manufacture of ceramics, catalysts, composite materials, refractory heat-shielding systems. The method for obtaining nanoscale multioxide of refractory metals includes three stages. At the first stage, a mixture of powders of refractory metals W-Ta-Nb-Mo-V-Zr-Cr-Ti of equiatomic composition is mechanically activated in an energy-intensive ball mill in an inert atmosphere with balls accelerating from 100 to 600 m/s ² with a duration of at least 5- 10 min. At the second stage, a target is obtained from the activated mixture of powders by spark plasma sintering (SPS) on the SPS Labox-1575 unit at a pressure of 20-80 MPa, a temperature of 700-1200°C and with an exposure of at least 5 min. At the third stage, laser ablation of the obtained target in distilled water is carried out by pulsed laser radiation of the fundamental harmonic of a neodymium Nd:YAG laser with a wavelength of 1064 nm and a pulse duration of 7 ns.

EFFECT: invention makes it possible to obtain a nanoscale multioxide, including all the above refractory metals, despite their different affinity for oxygen.

1 cl, 3 dwg, 1 tbl, 2 ex

Description

The invention relates to the field of obtaining metal oxides of complex composition from powder metal materials and can be used in technological cycles for obtaining precursors for the synthesis of ceramic compounds, the production of chemical catalysts, the creation of composite materials and elements of refractory heat-shielding systems for aerospace and rocket technology.

A known method of obtaining nanostructured powders for ceramics, synthesized by ultrasonic spray pyrolysis (A.V. Galakhov, L.V. Vinogradov, V.I. Antipov, A.G. Kolmakov Nanostructured powders for ceramics // Russian nanotechnologies. 2011. T. 6. No. 9-10, pp. 131-135).

The feedstock for obtaining powders are water-soluble (or soluble in organic liquids) compounds containing a set of components required for the synthesis of powder material with the required elemental and phase composition. Working solutions are converted into a gas suspension of micron-sized droplets using an ultrasonic aerosol generator. The formation of powder particles occurs during the pyrolysis of aerosol droplets transported through the hot zone of the through-flow reactor. In this case, the gas - the carrier of the aerosol - also performs the function of the active component of the reaction. In this way, ZrO ₂ +Y ₂ O ₃ powders with an average particle size of 0.8 μm and an average size of intraparticle grains of 26 nm were obtained.

A known method for the synthesis of nanosized oxides of niobium and tantalum (K.A. Smirnova, V.V. Fomichev, D.V. Drobot, E.E. Nikishina Obtaining nanosized niobium and tantalum pentoxides by the method of supercritical fluid antisolvent precipitation // Fine chemical technologies. 2015 10. No. 1. S. 76-82) from methyloids of the corresponding metals.

The presented method is based on the ability of carbon dioxide supercritical fluid to act as a precipitator of polar substances from non-polar solvents, and is used as a dispersion method to obtain micro- and nanoforms of substances. Using this method on a laboratory dispersion system SAS-50 (Thar Technologies), tantalum pentoxide particles with a size of 40 - 600 nm (the content of a nanosized fraction is less than 100 nm - 61%) and particles of niobium pentoxide with a size of 100 - 500 nm (content of ultrafine fraction 97%).

A known method for producing titanium dioxide using laser ablation (E.D. Fakhrutdinova, A.V. Shabalina, M.A. Gerasimova, A.L. Nemoykina, O.V. Vodyankina, V.A. Svetlichnyi Highly Defective Dark Nano Titanium Dioxide: Preparation via Pulsed Laser Ablation and Application // Materials. 2020. V. 13 No. 2054. P. 1-17).

A titanium target (99% Ti) was used as the starting material. Dispersions of titanium dioxide in water were obtained by pulsed laser ablation. The radiation of the fundamental harmonic of a Nd:YAG laser (LOTIS TII, model LS2131M-20) with a wavelength of 1064 nm was used. The pulse duration was 7 ns. The resulting solution was dried in air at a temperature of 60°C. In this way, TiO ₂ powders were obtained with a particle size in the range of 5 - 80 nm

The disadvantage of the presented analogs is the possibility of forming only individual oxides or mixtures of oxides of different metals.

The closest in technical essence to the solution chosen as a prototype is a method for obtaining nanosized mixed oxides of refractory metals using the citrate sol-gel method (A. Verma, R. Dwivedi, R. Prasad, KS Bartwal Microwave-Assisted Synthesis of Mixed Metal- Oxide Nanoparticles // Journal of Nanoparticles 2013 V 2013 Art ID 737831 http//dx.doi.org/10.1155/737831). Zirconium oxychloride, anhydrous citric acid, and titanyl nitrate were used as starting materials. These precursors were mixed and sufficient distilled water was added to obtain a homogeneous sol. The well-mixed solution was evaporated by exposing it to a microwave oven for 2 minutes. After drying, the material turned into a gel, which was further calcined in a tube furnace at a temperature of 400 ° C for 4 hours. Upon calcination, a precipitate was obtained, which was again triturated into a fine powder . As a result of the performed operations, ZrTiO ₄ particles with sizes up to 5 nm, combined into conglomerates, were obtained.

The disadvantage of the prototype is the possibility of obtaining oxides of only binary systems.

The objective of the present invention is to develop a method for obtaining nanoscale multioxides of refractory metals.

The technical result is the production of complex oxides, which simultaneously include all the components of the mixture, despite significant differences in the oxygen affinity of the various elements included in its composition.

The problem is solved by the fact that the proposed method for obtaining nanoscale multioxides of refractory metals includes three stages, in which:

- at the first stage, mechanical processing (activation) of a mixture of powders of refractory metals is carried out in an energy-intensive ball mill;

- at the second stage, spark plasma sintering (SPS) of said mixture of powders is carried out after their mechanical activation to obtain a target for its subsequent laser ablation;

- at the third stage, laser ablation of said target in distilled water is carried out by pulsed laser radiation of a neodymium Nd:YAG laser.

In this case, a mixture of W-Ta-Nb-Mo-V-Zr-Cr-Ti powders of equiatomic composition is used as powders of refractory metals.

In addition, mechanical processing (activation) of the mentioned powders in energy-intensive ball mills is carried out in an inert atmosphere with balls accelerating from 100 to 600 m/s ² for at least 5 to 10 minutes.

Moreover, spark plasma sintering of the mixture of the mentioned powders after their mechanical activation is carried out on the SPS Labox-1575 installation under pressure conditions of 20 - 80 MPa at a temperature of 700 - 1200°C and holding for at least 5 minutes.

While pulsed laser ablation of the said target is carried out using the radiation of the fundamental harmonic of a Nd:YAG laser with a wavelength of 1064 nm and a pulse duration of 7 ns.

The claimed method includes pulsed laser ablation of a metal target in distilled water, the target is produced by spark plasma sintering of a mixture of refractory metal powders after their mechanical activation.

Mechanical processing of the mixture is carried out in an inert atmosphere of argon, in a planetary ball mill.

The proposed method is carried out as follows.

Mechanical treatment (activation) of a mixture of W-Ta-Nb-Mo-V-Zr-Cr-Ti powders of equiatomic composition in an energy-intensive planetary ball mill. Loading and processing of the powder are carried out in an inert atmosphere with balls accelerating from 100 to 600 m/s ² for at least 5-10 minutes. The duration of mechanical activation, the load factor, the number and size of grinding media are selected depending on the characteristics of the ball mill. To limit the heating of the material during processing, the mill is equipped with water cooling or processing is carried out intermittently. Spark plasma sintering (SPS) of the mixture of powders after pretreatment by the indicated methods was carried out on an SPSLabox-1575 installation under pressure conditions of 20–80 MPa at a temperature of 700–1200°C and a holding time of at least 5 minutes.

The resulting preform of a multicomponent alloy was used as a target for pulsed laser ablation in distilled water. The radiation of the fundamental harmonic of a Nd:YAG laser with a wavelength of 1064 nm was used. The pulse duration was 7 ns.

Hereinafter, the present invention will be described by way of example with reference to the accompanying drawings, in which:

In FIG. 1 shows a TEM image of particles of nanosized multioxides obtained by the proposed method.

In FIG. 2 shows a microdiffraction image from particles of nanosized multioxides.

In FIG. Figure 3 shows the result of energy dispersive spectral analysis.

Example 1

A mixture of W-Ta-Nb-Mo-V-Zr-Cr-Ti powders was subjected to mechanical activation for 5 minutes in an AGO-2 planetary ball mill. When processing, steel equipment was used, an argon atmosphere, the centrifugal acceleration of the balls was 200 m/s ² . SPS was performed at a pressure of 30 MPa, a temperature of 1000°C, and an exposure of at least 10 minutes. Laser ablation was performed at a wavelength of 1064 nm and a pulse duration of 7 ns.

Example 2

A mixture of W-Ta-Nb-Mo-V-Zr-Cr-Ti powders was mechanically activated for 10 minutes in an AGO-2 planetary ball mill. When processing, steel equipment was used, an argon atmosphere, the centrifugal acceleration of the balls was 400 m/s ² . SPS was carried out at a pressure of 60 MPa, a temperature of 1200°C, and an exposure time of at least 10 minutes. Laser ablation was performed at a wavelength of 1064 nm and a pulse duration of 7 ns.

As shown in FIG. 1, after the proposed processing method, spherical particles are formed, the size of which is in the range from 10 to 80 nanometers. In FIG. Figure 2 shows the microdiffraction pattern from the presented particles, in which a halo characteristic of amorphous structures is observed.

The study showed that these particles are complex multioxides of refractory metals that were included in the initial mixture of powders (Fig. 3, table 1). It should be noted that there is a uniform distribution of elements over the volume of the material, although it is well known that alloys of refractory materials with a large difference in melting temperatures are characterized by separation of elements by atomic number during the formation of multicomponent compositions. In addition, the proposed method makes it possible to form complex oxides that simultaneously include all components of the mixture, despite significant differences in the oxygen affinity of various elements that make up it.

Table 1. Composition of particles of nanosized multioxides according to the results of energy dispersive spectral analysis Element Weight % Atomic% O 33.37 76.72 Ti 3.43 2.65 V 2.50 1.81 Cr 3.24 2.29 Zr 9.01 3.71 Nb 8.97 3.60 Mo 6.16 2.40 Ta 20.63 4.26 W 12.70 2.58

Claims (4)

A method for obtaining nanosized multioxides of refractory metals of the W-Ta-Nb-Mo-V-Zr-Cr-Ti system, consisting of three stages: - at the first stage, mechanical processing (activation) of a mixture of powders of refractory metals W-Ta-Nb-Mo-V-Zr-Cr-Ti of equiatomic composition is carried out in an energy-intensive ball mill in an inert atmosphere with balls accelerating from 100 to 600 m/s ² duration at least 5-10 minutes; - at the second stage, spark plasma sintering (SPS) of the above mixture of powders is carried out after their mechanical activation on the SPS Labox-1575 installation under pressure conditions of 20-80 MPa at a temperature of 700-1200°C and exposure for at least 5 minutes to obtain a target for its subsequent laser ablation; - at the third stage, laser ablation of said target in distilled water is carried out by pulsed laser radiation of the fundamental harmonic of a neodymium Nd:YAG laser with a wavelength of 1064 nm and a pulse duration of 7 ns.

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