RU2792036C1 - METHOD OF OBTAINING VANADIUM-ALUMINUM CARBIDE V2AlC USING SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS - Google Patents

Abstract

FIELD: powder metallurgy.

SUBSTANCE: invention relates to the field of powder metallurgy, in particular to the production of vanadium-aluminum carbide V₂AlC, referred to the MAX phase family materials, used in the chemical and metallurgical industries for the manufacture of parts operating at high temperatures in oxidizing environments and as precursors for obtaining electrode materials of lithium-ion and sodium-ion batteries. The method includes preparation of a blend of powders of vanadium (V) – V₂O₅, aluminum and carbon, loading into a graphite crucible, carrying out self-propagating high-temperature synthesis under argon pressure, while magnesium and sodium chloride are additionally introduced into the mixture, herewith soot is used as a source carbon, and the ration of components is as follows (% by weight): vanadium oxide (V) 22.2-31.2; aluminum 3.7-5.1; magnesium 23.5-32.9; carbon 0.6-0.8; sodium chloride 30-50; and self-propagating high-temperature synthesis is performed at an argon pressure of 3 MPa, then chemical leaching of the synthesis product is carried out in a 15% hydrochloric acid solution at a temperature of 90° C for 2 hours. The final product is a black powder, with a weight fraction of particles sized between 1 and 10 mcm equal to 80%. The particles have a scaly morphology.

EFFECT: content of the main substance V₂AlC is 95 % by weight, which is indicative of an increased purity.

1 cl, 2 dwg, 2 tbl, 2 ex

Description

The invention relates to the field of powder metallurgy, in particular to the production of vanadium-aluminum carbide V ₂ AlC by the method of self-propagating high-temperature synthesis. Vanadium aluminum carbide belongs to the family of MAX phases, materials based on which are used in the chemical and metallurgical industries for the manufacture of parts operating at high temperatures in oxidizing environments and as precursors for the production of electrode materials for lithium-ion and sodium-ion batteries.

From the scientific - technical literature known methods for producing vanadium - aluminum carbide V ₂ AlC, which are based on the methods of arc melting, hot pressing, sintering in a plasma discharge, microwave sintering, synthesis in the molten salts. Most of the known methods of synthesis involve the use of expensive vanadium powder as the initial component of the mixture and energy-intensive specialized equipment for heat treatment of the charge with the application of pressure.

A known method for producing vanadium - aluminum carbide V ₂ AlC by arc melting from a stoichiometric mixture of powders of vanadium, aluminum and carbon [Article "Schuster J. C, Nowotny H. and Vaccaro C. The ternary systems: Cr-Al-C, V-Al -C, and Ti-Al-C and the behavior of H-phases (M ₂ AlC) // J. Solid State Chem. 1980. V. 32. P. 213-219”]. After melting, the ingots are annealed in vacuum at temperatures from 600 to 1200°C for 170-500 hours.

The disadvantage of this method of obtaining vanadium - aluminum carbide V ₂ AlC are high energy costs for melting and long isothermal annealing of the material; low process productivity; significant cost of the charge, including powder of metallic vanadium.

A known method for producing vanadium - aluminum carbide V ₂ AlC by hot isostatic pressing from a stoichiometric mixture of powders of vanadium, aluminum and carbon black [Article "Gupta S., Barsoum MW Synthesis and oxidation of V ₂ AlC and (Ti _0.5 V _0.5 ) ₂ AlC in air // J. Electrochem. soc. 2004. V.151. R.24-29 "]. The charge is preliminarily annealed at 650°C for 10 hours, then heated at a rate of 10 deg/min to 650°C, 2 deg/min to 750°C and 10 deg/min to 1600°C in an argon atmosphere at a pressure of 40 MPa and subjected to hot isostatic pressing for 8 hours at a pressure of 100 MPa.

The disadvantage of this method of obtaining vanadium - aluminum carbide V ₂ AlC are high energy costs for heating and long-term sintering of the mixture; low process productivity; significant cost of the charge, including powder of metallic vanadium; presence in the final product up to 2 wt. % admixture of aluminum oxide, which worsens its physical and mechanical properties.

A known method for producing vanadium-aluminum carbide V ₂ AlC by sintering in a plasma discharge [Article "Hossein-Zadeh M., Mirzaee O., Mohammadian-Semnani H., Razavi M., Microstructure investigation of V ₂ AlC MAX phase synthesized through spark plasma sintering using two various sources V and V ₂ O ₅ as the starting materials // Ceram. Int. 2019. V.45. R.23902-23916”]. A mixture of powders of vanadium (V) oxide, aluminum and graphite in a molar ratio of 1:4.83:1 is mixed in ethanol for 10 minutes in a high-energy ball mill. Next, the mixture is placed in a graphite container and sintered in a plasma discharge at a temperature of 1350°C with a successive increase in pressing pressure from 10 to 30 MPa under a vacuum of 21 Pa. The total sintering time in the plasma discharge is 90 minutes.

The disadvantage of this method of obtaining vanadium - aluminum carbide V ₂ AlC are high energy costs for heating and sintering the mixture in the plasma discharge; a significant content of impurities of aluminum oxide, vanadium carbide and non-stoichiometric vanadium carbide.

A known method of obtaining vanadium - aluminum carbide V ₂ AlC by microwave sintering [Article "E. Ghasali, Y. Orooji, A. Azarniya, M. Alizadeh, and M. Kazem-zad, Production of V ₂ C MXene using a repetitive pattern of V ₂ AlC MAX phase through microwave heating of Al-V ₂ O ₅ -C system , Appl. Surf. sci. 542 (2021) 14853”]. A mixture of powders of vanadium (V) oxide, aluminum and carbon black in a molar ratio of 1:4.63:1 is mixed in ethanol for 20 minutes in a high-energy ball mill. A sample is pressed from the mixture, placed in a corundum mold and sintered in a microwave oven with a power of 900 W and a frequency of 2 GHz at a temperature of 1250°C.

The disadvantage of this method of obtaining vanadium - aluminum carbide V ₂ AlC is the significant content of impurities of aluminum oxide and non-stoichiometric vanadium carbide.

A known method for producing vanadium - aluminum carbide V ₂ AlC in molten salt [Article "C. Roy, P. Banerjee, S. Bhattacharyya, Molten salt shielded synthesis (MS3) of Ti ₂ AlN and V ₂ AlC MAX phase powders in open air, J. Eur. Ceram. soc. 40 (2020) 923-929”]. The mixture of powders of vanadium, aluminum and graphite in a molar ratio of 2:1.1:0.9 is mixed manually for 1 hour with salt flux NaCl:KCl = 1:1 in a weight ratio of 1:1. A sample is pressed from the mixture, placed in a corundum crucible and heated in air in a tubular furnace at a rate of 5 deg/min to a temperature of 1100°C and annealed for 1 hour. After cooling, the sample is ground and washed with deionized water for 30-45 minutes to remove the salt flux. The result is a powder of vanadium - aluminum carbide V ₂ AlC purity 82 wt. %.

The disadvantage of this method of obtaining vanadium - aluminum carbide V ₂ AlC are the presence of aluminum oxide impurities in the material in the amount of 4 wt. % and graphite in the amount of 14 wt. %; significant cost of the charge, which includes powder of metal vanadium.

Known patent [CN 101486576 (A) - C04B 35/56 - 2009-07-22. In situ reaction heat pressing synthesized V ₂ AlC bulk ceramic and preparation thereof] to obtain dense ceramic V ₂ AlC, according to which a charge is prepared from powders of vanadium, aluminum and carbon black, mixed for 12-24 hours, dried and placed in a graphite mold , then sintered in a hot pressing furnace in vacuum or argon at a temperature of 1400-1700°C for 30-60 minutes with a pressing pressure of 25-35 MPa.

The disadvantages of this method of obtaining vanadium - aluminum carbide V ₂ AlC are: low productivity of the process due to the use of additional operations for mixing the original powders; high energy costs for heating and sintering the mixture, as well as a significant cost of the charge, including metal vanadium powder.

Known patent [CN 112591752 (A) - C01B 32/90; H01M 10/0525; H01M 10/054; H01M 4/587; H01M 4/62 - 2021-04-02. Method for rapidly preparing V ₂ AlC powder by utilizing molten salt chemical reaction and application of V ₂ AlC powder] according to which the method for producing vanadium-aluminum carbide V ₂ AlC is two-stage. At the first stage, a mixture of vanadium powder with carbon black is prepared in a molar ratio of 1.98:2.0. From this mixture and salt/salts of alkaline earth metals (LiCl, KCl, CaCl ₂ -NaCl, NaCl-KCl, LiCl-KCl, LiCl-KCl-NaCl, KF-KCl, LiF-KF, LiCl-KCl-CaCl ₂ ) in mass in a ratio of 1:1, a mixture is prepared, loaded into a corundum crucible, placed in an oven with an inert atmosphere, heated to 800-1000 ° C and incubated for 2 hours, then the product is cooled and ground. At the second stage, aluminum powder in the molar ratio V ₂ C:Al=1:1.2 is added to the obtained powder containing the V ₂ C precursor. The mixture in a corundum crucible is placed in a furnace, heated to 800-1000°C in an inert atmosphere and kept for 2 hours. After cooling, the product is ground, washed with water to remove salts and dried.

The disadvantages of this method of obtaining vanadium - aluminum carbide V ₂ AlC are the energy costs for heating and two-stage isothermal exposure of the mixture and the significant cost of the charge, including powder of metallic vanadium.

Known patent [CN 113336553 (A) - SW 35/56; С04В 35/622; С04В 35/65 - 2021-09-03. V ₂ AlC block material synthesized by microwave sintering as well as preparation method and application of V ₂ AlC block material] to obtain dense ceramics V ₂ AlC, in accordance with which the following operations are performed: powders of vanadium, aluminum and graphite are taken in the molar ratio V: Al:C=2:(1.1-1.4):1, sintering additive LaF ₃ or CeF ₃ is added, mixed in ethanol for 30 minutes, dried in vacuum for 5 hours at a temperature of 50°C; a cylindrical sample is pressed from the mixture at a pressure of 240 MPa; placed in a microwave oven and heated to 1250°C in an argon atmosphere, incubated for 5 minutes.

The disadvantages of this method of obtaining vanadium - aluminum carbide V ₂ AlC are the energy costs for heating and isothermal exposure of the mixture and the significant cost of the charge, including powder of metallic vanadium.

The closest in technical essence to the claimed invention is a method for producing vanadium - aluminum carbide V ₂ AlC by the method of self-propagating high-temperature synthesis at a temperature exceeding the melting temperature of all compounds of the V-Al-C system [Article "Gorshkov V.A., Karpov A.V. , Kovalev D.Yu., Sychev A.E. Synthesis, structure and properties of a material based on the MAX-phase V ₂ AlC // Physics of metals and metallurgy. 2020. V.121. No. 8. S.842-848»]. In this method, a charge is prepared from a mixture of powders of vanadium (V) oxide, vanadium (IV) oxide, aluminum and graphite in a mass ratio of 48:11:37:4, mixed manually and placed in a graphite crucible. Synthesis is carried out in a sealed reactor in an argon atmosphere at a pressure of 5 MPa by initiating an exothermic chemical reaction from a spiral. After cooling, oxide slag is mechanically separated from the resulting ingot. The disadvantage of this prototype is the presence in the resulting material 35 wt. % impurities - vanadium intermetallides VAl, VAl ₃ and vanadium carbides VC and V ₂ C.

The technical result of the proposed method is to increase the purity of the powder of vanadium - aluminum carbide V ₂ AlC, reduce energy costs and increase the productivity of its production.

The technical result is achieved by the fact that the method for producing vanadium-aluminum carbide V ₂ AlC by the method of self-propagating high-temperature synthesis includes preparing a charge from a mixture of powders of vanadium (V) oxide, aluminum and carbon, loading into a graphite crucible, carrying out self-propagating high-temperature synthesis, magnesium is additionally introduced into the mixture and sodium chloride, and carbon black is taken as a carbon source, in the following ratio, wt. %)

vanadium(V) oxide 22.2 - 31.2 aluminum 3.7-5.1 magnesium 23.5-32.9 carbon 0.6-0.8 sodium chloride 30-50,

while self-propagating high-temperature synthesis is carried out at an argon pressure of 3 MPa, then chemical leaching of the synthesis product is carried out in a 15% hydrochloric acid solution at a temperature of 90°C for 2 hours.

The essence of the invention is as follows. A mixture is prepared from a mixture of powders of vanadium (V) oxide grade HCh in the amount of 22.2-31.2 wt. %, aluminum brand ASD-4 in the amount of 3.7-5.1 wt. %, magnesium grade MPF in the amount of 23.5-32.9 wt. %, soot brand P804-T in the amount of 0.6-0.8 wt. % and sodium chloride grade KhCh in the amount of 30-50 wt. %. The preparation of the charge from a mixture of powders is carried out in a ball mill in air for 2 hours at a mass ratio of charge and stainless steel balls 1/3. The mixture in a graphite crucible is placed in a reactor, washed 2 times with argon and filled with argon at a pressure of 3 MPa, then the mixture is ignited with a tungsten coil, an exothermic reaction of self-propagating high-temperature synthesis takes place. The use of soot rather than graphite as a carbon source is associated with the high reactivity of soot due to the large specific surface area. During combustion, exothermic chemical reactions take place:

The burning time does not exceed 60 seconds, and the total time of operations, including charge loading and product cooling, does not exceed 1 hour. After cooling, the product is removed from the reactor and ground in succession in a jaw crusher and in a roller ball mill. After synthesis, the material contains vanadium - aluminum carbide, magnesium oxide, magnesium, vanadium aluminide, vanadium carbide and sodium chloride (table 1). Side compounds - magnesium oxide, vanadium aluminide and magnesium are soluble in hydrochloric acid.

Conduct chemical leaching of the intermediate in a 15% hydrochloric acid solution at a temperature of 90°C for 2 hours. The following chemical reactions take place, leading to the formation of water-soluble salts of vanadium and aluminum:

Washing the product from salts of vanadium, aluminum and sodium chloride is carried out in distilled water. The result is vanadium-aluminum carbide V ₂ AlC purity 95 wt. %, which is confirmed by the data of X-ray phase analysis - diffraction pattern of the product after acid leaching (Fig. 1).

When the content of vanadium oxide is less than 22.2 wt. %, the combustion process in the SHS mode does not occur due to the lack of heat during the reduction of vanadium oxide with magnesium, when the content of vanadium oxide is more than 31.2 wt. % remains unreduced vanadium oxide in the synthesis product, this degrades the quality of the product, with an aluminum content of less than 3.7 wt. % V ₂ AlC is not formed due to lack of aluminum, with an aluminum content of more than 5.1 wt. % in the final product of synthesis, in addition to V ₂ AlC, V _x -Al _y compounds of different composition are formed, with a magnesium content of less than 23.5 wt. %, there is a lack of magnesium reducing agent, which leads to the formation of MgAl ₂ O ₄ spinel, which does not dissolve in mineral acids, contaminating the final product, when the magnesium content is more than 32.9 wt. %, the combustion process does not occur, since the heat of reaction is used to heat the excess magnesium not participating in the reaction, with a carbon content of less than 0.6 wt. % V ₂ AlC mode SHS is not formed, with a carbon content of more than 0.8 wt. %, carbides and intermetallic compounds of vanadium and different compositions are formed (VC, V ₂ C and VA1, VA1 ₃ ), with a sodium chloride content of less than 30 wt %, V ₂ AlC and VC are formed, and the content of VC is much higher than V ₂ AlC, with a content sodium chloride more than 50 wt. %, the combustion process in the SHS mode does not occur due to the large amount of heat used to heat the inert sodium chloride additive. The essence of the proposed method is confirmed by examples.

Example 1. Take 44.4 g of powdered vanadium oxide chemical pure (22.2 wt.%); 7.4 g of ASD-4 brand aluminum powder (3.7 wt. %); 47 g of magnesium powder grade MPF-3 (23.5 wt.%); 1.2 g of carbon black powder grade P804T (0.6 wt.%) and 100 g of sodium chloride of chemical purity (50 wt.%).

The powders are loaded into a stainless steel ball mill drum and mixed for 2 hours. Then the prepared mixture is loaded into a graphite crucible. The crucible with the mixture is placed in a sealed reactor, closed, purged 2 times with argon and filled with argon to a pressure of 3 MPa, the mixture is ignited with a tungsten coil, after 60 s, combustion stops. The reactor with the contents is cooled for 30 minutes. The reaction product is unloaded from the graphite crucible, crushed in a jaw crusher, crushed in a ball mill for 30 minutes and treated in a 15% hydrochloric acid solution at a temperature of 90°C for 2 hours. Then filtered, washed in distilled water and dried.

Example 2. Under the conditions of example 1, characterized in that they take 49 g of vanadium oxide powder of chemical purity (24.5 wt.%); 8 g of ASD-4 grade aluminum powder (4 wt %)); 51.8 g of magnesium powder grade MPF-3 (25.9 wt.%); 1.2 g of carbon black powder grade P804T (0.6 wt.%) and 90 g of sodium chloride of chemical purity (45 wt.%).

The final product is a black powder, in which the weight fraction of particles with a size of 1 μm to 10 μm is 80% (Fig. 2a). The particles have a scaly morphology (Fig. 2b). The content of the main substance V ₂ AlC is 95 wt. %.

All examples are summarized in table 1

Table 2 shows the phase composition of the product before and after acid leaching, wt. %.

Claims (3)

A method for producing vanadium-aluminum carbide V ₂ AlC, including preparing a charge from a mixture of powders of vanadium (V) oxide, aluminum and carbon, loading into a graphite crucible, carrying out self-propagating high-temperature synthesis at argon pressure, characterized in that magnesium and chloride are additionally introduced into the mixture sodium, and carbon black is taken as a source of carbon, with the following ratio of components, wt.%: vanadium(V) oxide 22.2-31.2 aluminum 3.7-5.1 magnesium 23.5-32.9 carbon 0.6-0.8 sodium chloride 30-50, at the same time, self-propagating high-temperature synthesis is carried out at an argon pressure of 3 MPa, then chemical leaching of the synthesis product is carried out in a 15% hydrochloric acid solution at a temperature of 90°C for 2 hours.

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