Method for producing porous high-entropy alloy

Abstract

FIELD: powder metallurgy.SUBSTANCE: invention relates to high-entropy alloys. The invention can be used for the synthesis of carbon nanostructures, including carbon nanotubes, as catalysts for the production of intermediate compounds and final products of organic synthesis with high added value. The method for producing a porous high-entropy alloy includes preparing a mixture of powders of copper, nickel, cobalt formates, zinc formate or oxalate, and iron oxalate in a molar ratio of 1:1:1:1:1, making tablets in a press mould, placing them in a quartz retort, and heat treating the tablets in a stream of hydrogen while heating the tablets from 20 °C a rate of 5-50 degrees / min to a final temperature in the range of 600-700 °C, while heating is stopped for 10-15 minutes at temperatures of decomposition of organic metal salts.EFFECT: ensuring the production of a high-entropy alloy with high porosity and uniform distribution of metals throughout the volume of the alloy.5 cl, 7 tbl, 4 ex

Description

[0001] Promising areas of application for high-entropy alloys include biomedicine, the creation of materials with special magnetic properties, including those with a magnetocaloric effect, the aerospace industry, welding, the creation of superconductors, and catalysis.

[0002] The invention relates to powder metallurgy, specifically to high-entropy alloys. It can be used to synthesize carbon nanostructures, including carbon nanotubes, as catalysts for producing intermediate compounds and end products of organic synthesis with high added value.

[0003] The aim of the invention is to create a new porous high-entropy alloy at a temperature below the melting points of the metals that make it up, for use as a metal catalyst.

[0004] A method for producing a high-entropy alloy is known. The method involves smelting the alloy, Fe 38 Mn40 Co 10 Cr 10 N2, cold rolling, and subsequent annealing using vacuum arc remelting. The alloy after deformation and heat treatment has high strength and ductility (RU 279070, C22F 1 / 16, C22C 38 / 30, C22C 30 / 00, C21D 8 / 00, 28.02. 2023).

[0005] Another method for producing a high-entropy alloy pertains to powder metallurgy, specifically to methods for producing high-entropy shape-memory alloy powders. It can be used for general metallurgical applications and additive manufacturing. Elemental powders of Ti, Ni, Hf, Co, Cu, and Zr are mixed in air, and Zr powder is added in a high-purity argon atmosphere. The resulting mixture is processed in an attritor with the addition of grinding media and isopropyl alcohol under an inert atmosphere to produce a pre-alloyed powder. Spheroidization is performed in a low-temperature plasma stream using a plasma-forming mixture of argon and hydrogen gases at a plasma torch power of up to 15 kW, followed by cooling in an argon stream. This ensures the production of a powder of pore-free spherical particles with high fluidity and a uniform chemical composition. (RU 2776112, B22F 9 / 14, B22F 1 / 00, 1.09 2022).

[0006] One of the most studied systems is the Co-Cr-Fe-Mn-Ni system. The equiatomic alloy CoCrFeMnNi, described in [Cantor et al. Microstructural development in equiatomic multicomponent alloys, Materials Science and Engineering A, 2004, v. 375-377, pp. 213-218], is produced by induction melting of pure elements in equal atomic proportions in an Al2O3 crucible under Ar pressure. Deformation-heat treatment leads to a significant increase in strength with high ductility over a wide temperature range [Otto et al. The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy, Acta Mater, 2013, v. 61, pp. 5743-5755].

[0007] All the described methods for producing high-entropy alloys require melting the source metals, resulting in very low porosity of the alloys. The proposed method for producing a high-entropy alloy eliminates the need for melting the source metals, achieving high porosity and uniformity of alloy composition.

[0008] The closest to the proposed technical solution is a method for producing porous metals, alloys and pseudoalloys, which includes preparing a mixture of powders of one or two organic salts of copper, nickel, iron, cobalt from a number of formates, oxalates, citrates, acetates of the listed metals in a molar ratio of 0.1:1 to 1:0.1, producing tablets in a press mold, placing them in a quartz retort and heat treating the tablets in a hydrogen stream while heating the tablets at a given rate from 20 °C to a final temperature in the range of 400-900 °C, heating is stopped for 5-15 minutes at the decomposition temperatures of the organic salts (RU 2815844, B22A311, B22F 3 / 11, C22C 1 / 082, 22.03.2024).

[0009] However, the technical result of this method involves no more than two metals.

[0010] The technical result of the proposed method is an increase in porosity and uniformity of distribution of metals throughout the entire volume of the high-entropy alloy.

[0011] The technical result is achieved in that the method for producing a porous high-entropy alloy includes preparing a mixture of powders of copper, nickel, cobalt formates, zinc formate or oxalate and iron oxalate in a molar ratio of 1:1:1:1:1, producing tablets in a press mold, placing them in a quartz retort and heat treating the tablets in a stream of hydrogen while heating the tablets from 20°C at a rate of 5-50 deg / min to a final temperature in the range of 600-700°C, while the heating is stopped for 10-15 minutes at the temperatures of decomposition of organic metal salts.

[0012] The essence of the proposed method is as follows. A mixture of copper, nickel, cobalt formate powders, zinc formate or oxalate and iron oxalate is prepared, tablets are prepared in a press mold. The resulting tablets 1 are placed in a quartz boat 2 and then in a gas-tight quartz retort 3 for heat treatment of tablets in a gas flow, 4 is a gas inlet tube, 5 is a gas outlet tube. (Fig. 1) and heat treatment is carried out in a hydrogen flow while heating the tablets from 20 °C at a rate of 5-50 deg / min to a final temperature in the range of 600-700 °C, heating is stopped for 5-15 min at the decomposition temperatures of organic salts. Then the retort is cooled to room temperature and porous tablets with a metallic luster are removed.

[0013] The required tablet porosity is achieved by varying the final heating temperature. Commercial, chemically pure organic salts are used.

[0014] If the equimolarity ratio for any of the components is violated, the resulting tablet will crumble, which will not lead to the technological result.

[0015] The use of five organic salts of nickel, cobalt, copper, zinc and iron in the initial mixture makes it possible to obtain a high-entropy alloy with high permeability and uniformity throughout the entire volume of the alloy.

[0016] The proposed method makes it possible to obtain a high-entropy alloy, which is an interweaving of chains of alloy particles, with the average distance between the chains being 0.5-1 μm.

[0017] The essence of the proposed method is confirmed by the following example.

[0018] Example 1. The initial mixture of powders of four formates of copper, nickel, cobalt, zinc and iron oxalate in a molar ratio of 1:1:1:1:1 in an amount of 3 g is placed in a press mold with a diameter of 13 mm and pressed, selecting the pressure so that the tablets are free of cracks and chips. The resulting tablets 1 are placed in a quartz boat 2 and then in a gas-tight quartz retort 3 for heat treatment of the tablets in a gas flow, 4 is a gas inlet tube, 5 is a gas outlet tube. (Fig. 1). The retort is placed in an electric furnace and purged with argon at a flow rate of 1 l / min for 5 min. Then heating is turned on at a rate of 5 deg / min and purged with hydrogen at a flow rate of 1 l / min during the entire process of heat treatment and cooling. Heating is programmed so that upon reaching the decomposition temperature of cobalt formate (175°C), copper formate (200°C), nickel formate (210°C), zinc formate (250°C), and iron oxalate (190°C), the furnace temperature does not change for 10 minutes.The final temperature of 650°C is maintained for 30 min, then the furnace is turned off, the reactor is cooled to room temperature under an argon stream, and the pellets are removed. The material consists of an intertwined chain of high-entropy alloy particles (see Table 6 for composition) with an average diameter of 800 nm, and an average distance between chains of 1000 nm (Fig. 2). The density of the pellets was 2.25 g / cm3. 3 , is determined by the formula ρ = m / V, where m is the mass of the tablet, V is the volume of the tablet. The porosity of tablets P is determined by the formula P = 1 - ρ / ρ т , where ρ т =8.34 g / cm 3 - theoretical density of a non-porous high-entropy alloy. The estimated porosity of the tablet material is 73%. The measured volumetric shrinkage of the sample was 72%.

[0019] Example 2. The initial powder mixture of three formates of copper, nickel, cobalt, zinc oxalate and iron oxalate in a molar ratio of 1:1:1:1:1 in an amount of 3 g is placed in a press mold with a diameter of 13 mm and pressed, selecting the pressure so that the tablets are free of cracks and chips. The resulting tablets are placed in a gas-tight quartz retort for heat treatment of the tablets in a hydrogen stream. (Fig. 1). The retort is placed in an electric furnace and purged with argon at a flow rate of 1 l / min for 5 min. Then, heating is turned on at a rate of 40 deg / min, and hydrogen is purged at a flow rate of 1 l / min throughout the entire process of heat treatment and cooling. Heating is programmed so that upon reaching the decomposition temperature of cobalt formate (175°C), copper formate (200°C), nickel formate (210°C), zinc oxalate (220°C), and iron oxalate (190°C), the furnace temperature does not change for 15 minutes.The final temperature of 600°C is maintained for 30 min, then the furnace is turned off, the reactor is cooled to room temperature under an argon stream, and the pellets are removed. The material consists of an intertwined chain of high-entropy alloy particles (see Table 3 for composition) with an average diameter of 800 nm, and an average distance between chains of 1000 nm (Fig. 3). The density of the pellets is 2.1 g / cm3. 3 is determined by the formula ρ=m / V, where m is the mass of the tablet, V is the volume of the tablet. The porosity of tablets P is determined by the formula P=1-ρ / ρ т , where ρ т =8.34 g / cm 3 - theoretical density of a non-porous high-entropy alloy. The estimated porosity of the tablet material is 75%. The volumetric shrinkage of the sample was 76%.

[0020] Example 3. The initial powder mixture of four formates of copper, nickel, cobalt, zinc and iron oxalate in a molar ratio of 1:1:1:1:1 in an amount of 3 g is placed in a press mold with a diameter of 13 mm and pressed, selecting the pressure so that the tablets are free of cracks and chips. The resulting tablets are placed in a gas-tight quartz retort for heat treatment of the tablets in a hydrogen stream. (Fig. 1). The retort is placed in an electric furnace and purged with argon at a flow rate of 1 l / min for 5 min. Then, heating is turned on at a rate of 50 deg / min, and hydrogen is purged at a flow rate of 1 l / min throughout the entire process of heat treatment and cooling. Heating is programmed so that upon reaching the decomposition temperature of cobalt formate (175°C), copper formate (200°C), nickel formate (210°C), zinc formate (250°C), and iron oxalate (190°C), the furnace temperature does not change for 12 minutes.The final temperature of 650°C is maintained for 30 min, then the furnace is turned off, the reactor is cooled to room temperature under an argon stream, and the pellets are removed. The material consists of an intertwined chain of high-entropy alloy particles (see Table 6 for composition) with an average diameter of 800 nm, and an average distance between chains of 1000 nm (Fig. 2). The density of the pellets was 2.35 g / cm3. 3 is determined by the formula ρ = m / V, where m is the tablet mass and V is the tablet volume. The estimated porosity of the tablet material is 65%. The measured volumetric shrinkage of the sample was 75%.

[0021] The following example shows the use of the obtained high-entropy alloy as a catalyst for producing carbon nanotubes.

[0022] Example 4. The initial powder mixture of four formates of copper, nickel, cobalt, zinc, and iron oxalate in a molar ratio of 1:1:1:1:1 in an amount of 1 g is placed in a 13 mm diameter press mold and pressed, selecting a pressure so that the tablets are free of cracks and chips. The resulting tablets are placed in a gas-tight quartz retort for heat treatment of the tablets in a hydrogen stream (Fig. 1). The retort is placed in an electric furnace and purged with argon at a flow rate of 1 l / min for 5 min. Then, heating is turned on at a rate of 30 deg / min, and hydrogen is purged at a flow rate of 1 l / min throughout the entire heat treatment and cooling process. Heating is programmed so that upon reaching the decomposition temperature of cobalt formate (175°C), copper formate (200°C), nickel formate (210°C), zinc formate (250°C), and iron oxalate (190°C), the furnace temperature does not change for 15 minutes.The final temperature of 600°C is maintained for 30 minutes, then the furnace is turned off, the reactor is cooled to room temperature under a flow of argon, and the pellets are removed. A high-entropy alloy pellet is placed in the pencil flame of a Luxlite XHG700 НС6 rubber SP 9703 propane-butane-air torch and heated to red-hot. The hot pellet is then placed in the yellow flame of a GB 2001 piezo torch for 30 seconds. The pellet is then cooled.

[0023] From the micrograph of the tablet surface, it can be seen that two-dimensional chains of single-walled carbon nanotubes with a thickness of ~10 nm with a small variation in thickness are formed on the tablet surface (Fig. 4). It can also be seen that these carbon nanotubes uniformly cover the surface of the high-temperature alloy (Fig. 5).

[0024] The results of XRD analysis of the tablet material (composition as in Table 1) show that the composition of the surface layer of the porous high-temperature alloy samples includes 92.48 wt.% carbon (Table 7).

[0025] The results of X-ray fluorescence analysis of the tablet material are summarized in Tables 1-6. It is evident that the surface layer composition of the porous high-entropy alloy samples is the same in the synthesis temperature range of 600-700°C.

[0026] Copper, nickel, cobalt, zinc formates and iron oxalate 1:1:1:1:1, final temperature 600°C.

[0027]

[0028] Copper, nickel, cobalt, zinc formates and iron oxalate 1:1:1:1:1, final temperature 700°C

[0029]

[0030] Copper, nickel, cobalt formates, zinc oxalate and iron oxalate 1:1:1:1:1, final temperature 600°C

[0031]

[0032] Copper, nickel, cobalt formates, zinc oxalate and iron oxalate 1:1:1:1:1, final temperature 700°C

[0033]

[0034] Copper, nickel, cobalt, zinc formates and iron oxalate 1:1:1:1:1, final temperature 700°C

[0035]

[0036] Copper, nickel, cobalt, zinc formates and iron oxalate 1:1:1:1:1, final temperature 650°C

[0037]

[0038] Composition of the surface layer of porous high-temperature alloy samples in the production of carbon nanotubes

[0039]

[0040] Thus, the proposed set of features of the invention makes it possible to obtain, in one technological stage, a porous high-entropy alloy with a pore size of about 1000 nm and with a uniform distribution of metals throughout the entire volume of the alloy.

[0041] The proposed method does not require melting of the source metals; the synthesis of a porous high-entropy alloy is achieved through the self-assembly of metal nanoparticles formed during the thermal decomposition of organic metal salts.

[0042] The obtained porous high-entropy alloy can be used in catalytic chemistry for the synthesis of carbon nanostructures, including carbon nanotubes, in the production of catalysts for the production of intermediate compounds and final products of organic synthesis with high added value.

[0043] All the described prototypes for producing high-entropy alloys require melting the original metals, while the porosity of these alloys is very low, and in this method, a high-entropy alloy with high porosity is obtained at a temperature below the melting temperatures of the metals that make it up.

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