RU2771498C1 - Method for producing nanosized nickel ferrite powder - Google Patents

Abstract

FIELD: powder metallurgy.SUBSTANCE: invention relates to powder metallurgy, in particular, to the production of nanosized nickel ferrite powder. The obtained powder can be used as high-density information carriers, ferromagnetic liquids, medical drug delivery vehicles, in various microwave devices and switching devices. The reaction solution is prepared by dissolving a mixture of salts of nitrates or chlorides of nickel and iron (III), taken in a molar ratio of 1:2, in a 10% solution of dextran 40. The mixture is stirred with a strongly basic gel anion exchange resin AB-17-8 in hydroxyl form at a temperature of 60°C within 1.5 hours. The precipitate is separated from the solution and dried at a temperature of 80°C for 2 hours, and firing is carried out at a temperature of 650°C for 3 hours.EFFECT: improvement of the quality of the target product due to the production of a single-phase nanosized product and simplification of production due to the elimination of additional stages of purification and washing of the precipitate.1 cl, 2 ex, 3 dwg

Description

The invention relates to a method for producing nanoparticles of nickel ferrite with a spinel structure, which can be used as high-density information carriers, ferromagnetic fluids, delivery vehicles for medical preparations, in various microwave devices and switching devices.

A known method of obtaining nickel ferrite solid-phase method [A. Azizi, SKSadrnezhaad. Effects of annealing on phase evolution, microstructure and magnetic properties of mechanically synthesized nickel-ferrite. ceramics international. 2010, V. 36, No. 7, P. 2241–2245], in which the initial substances NiO and b-Fe ₂ O _{3 were} mixed in a ratio of 1: 1 and ground for 8 hours on a planetary mill, then the resulting powder was subjected to heat treatment at 700°C for 1 hour. According to X-ray phase analysis, a pure nickel ferrite phase with particles 24 nm in size was formed.

The disadvantage of this method is the low quality of nickel ferrite, tk. the resulting product is contaminated with the material of the grinding media.

A known method of obtaining Nickel ferrite Sol-gel method [M.V. Kuznetsov, Yu.G. Morozov, O.V. Belousov. Levitation-jet synthesis of nickel ferrite nanoparticles. inorganic materials. 2012. V. 48, No. 10. S. 1172 - 1180]. An aqueous solution of nickel (0.4 M) and iron (0.8 M) nitrates was mixed with a solution of polyacrylic acid (PAA). With constant stirring, an appropriate amount of nitric acid was slowly added to this solution until pH 1-3. The resulting solution was evaporated until a clear sol formed, then heated at 50°C for 10 hours to further remove water. Next, the obtained gel was calcined at 400°C for 2 h. According to the results of X-ray phase analysis, a pure crystalline phase of nickel ferrite spinel was formed. According to TEM data, the average particle size was 20 nm.

The disadvantages of the sol-gel method include the complexity of the technology, namely, the duration of the synthesis process, the use of expensive reagents, and the complexity of controlling the particle size.

A known method of obtaining nickel ferrite by solvothermolysis [A. Hassan, M. A. Khan, M. Shahid et al. Nanocrystalline Zn ₁ –xCo _0.5x Ni _0.5x Fe ₂ O ₄ Ferrites: Fabrication via Co-Precipitation Route with Enhanced Magnetic and Electrical Properties. 2015. Vol. 393. P.56-61]. Nickel and iron chlorides were dissolved in ethylene glycol with stirring; after the color change, sodium acetate was added to the solution, the resulting mixture was poured into an autoclave and kept for 24 h at 200°C. The resulting precipitate was separated by centrifugation, dried and calcined at 600°C for 4 hours. The XPA data indicate the formation of a pure nickel ferrite phase, however, according to the XPS data, the samples are contaminated with carbon. The particles are spherical agglomerates about 150 nm in size, consisting of smaller particles with a diameter of about 10 nm.

The disadvantages of the solvothermal synthesis method are the duration and complexity of the method, as well as the low quality of the obtained nickel ferrite samples due to their contamination with iron oxides.

The closest technical solution for the purpose of the proposed method is a method of obtaining nickel ferrite by deposition [K. Maaz, S. Karim, A. Mumtaz et al. Synthesis and magnetic characterization of nickel ferrite nanoparticles prepared by co-precipitation route. Journal of Magnetism and Magnetic Materials. 2009. No. 321. P. 1838 - 1842]. Equal volumes of aqueous solutions of 0.2 M nickel chloride and 0.4 M iron (III) chloride are used as initial substances, and sodium hydroxide is used as a precipitant. A 3 M sodium hydroxide solution is added dropwise to the initial salt solutions to pH 12. Then, oleic acid is added to the reaction vessel to prevent atmospheric air oxidation and particle agglomeration. The resulting mixture was stirred for 40 minutes at 80°C. The precipitate separated by centrifugation is calcined for 10 hours at temperatures of 600-1000°C. According to the results of X-ray phase analysis, pure powders of nickel ferrite were obtained. According to transmission electron microscopy, the particle size increased with increasing temperatures.

The disadvantages of this method include its complexity and labor intensity, namely: the need for long-term washing and purification of the precipitate obtained from anions and cations of the precipitant, the multi-stage synthesis process, and the need for many hours of sample calcination.

The objective of the invention is to develop a simple, easy-to-use method for obtaining with improved characteristics of the target product.

The technical result of the invention:

- simplification of the method by eliminating additional stages of purification and washing of the precipitate;

- improving the quality of the target product by obtaining a single-phase nanoscale product.

The technical result of the invention is achieved by the fact that in the method for obtaining a nanosized powder of nickel ferrite, including the preparation of a reaction solution from a mixture of salts of nickel and iron (III) chlorides taken in a molar ratio of 1:2, obtaining a precipitate in the form of a powder, separating it, drying and firing , according to the invention, the reaction solution is prepared by dissolving a mixture of salts of chlorides or nitrates of nickel and iron (III), in a 10% solution of dextran 40; form at a temperature of 60°C for 1.5 hours, and firing is carried out at a temperature of 650°C for 3 hours.

Comparative analysis of the claimed invention and the prototype shows that the distinguishing features of the invention:

- chlorides or nitrates of nickel and iron (III) are used as salts;

- mixtures of salts are dissolved in a 10% solution of dextran 40;

- as a precipitant take strongly basic gel anion exchanger AB-17-8 in hydroxyl form;

- precipitation is carried out at a temperature of 60°C for 1.5 hours;

- firing is carried out at a temperature of 650°C for 3 hours.

In the claimed invention, the AV-17-8 anion exchange resin is used as a precipitant - a strongly basic anion exchange resin with a polystyrene matrix containing residues of Quaternary ammonium bases - N ⁺ (CH ₃ ) ₃ (GOST 20301-74).

Thanks to these distinctive features, it was possible to obtain nickel ferrite of stoichiometric composition. In addition, the proposed method leads to the formation of a nanoscale product.

The inventive method is carried out as follows.

Anion exchange resin AB-17-8 is prepared in hydroxyl form. The original AB-17-8 in the chloride form is poured with 1 M NaOH solution (m:l = 1:3), then with 2 M NaOH solution 3 times, keeping each portion for 1 hour. Next, the anion exchange resin is washed with distilled water until a negative reaction to the chloride ion, dried at a temperature of about 60°C, and before use, a sample of the anion exchange resin is poured for 5 minutes with distilled water to swell.

A reaction solution is prepared from a mixture of salts of chloride or nitrate of nickel and iron (III) in a molar ratio of 1:2. Next, the mixture of salts is dissolved in a 10% dextran solution. A weighed amount of anionite AB-17-8 is added to the resulting mixture, calculated by the formula:

where C _Ni 2+ , C _Fe ³⁺ is the concentration of initial solutions of nickel and iron (III);

V _Ni ²⁺ , V _Fe ³⁺ - volume of initial solutions of nickel and iron (III);

SOE - static exchange capacity, mmol-equiv⋅g ^-1 ;

n ₁ \u003d 3 (n ₂ \u003d 4.5) is the molar ratio of the functional groups of the ion exchanger and Ni ²⁺ (Fe ³⁺ ) ions.

The precipitation process is carried out with stirring on a shaker at a speed of 120 min.^-one at a temperature of 60°C for 1.5 hours. The anion exchanger is then separated by passing the mixture through a 0.16 mm sieve. For sediment separation filtered under vacuum. The resulting precipitate is dried at a temperature of 80°C in an oven and fired at a temperature of 650°C for 3 hours.

The invention is illustrated by drawings. Figure 1 shows the x-ray spectrum of a sample of Nickel ferrite obtained from solutions of chloride salts of Nickel and iron (III). In FIG. Figure 2 shows a micrograph of a sample of nickel ferrite obtained from solutions of chloride salts of nickel and iron (III). In FIG. Figure 3 shows the dependence of magnetic-circular dichroism on the magnitude of the magnetic field for nickel ferrite.

On the fig. 1 shows the X-ray spectra of the precipitation products fired at 650°C. In both cases, radiograph peaks <4.812>, <2.947>, <2.513>, <2.406>, <2.084>, <1.701>, <1.604>, <1.473>, <1.409>, <1.318>, <1.271>, <1.257> are characteristic of nickel ferrite. The maxima characteristic of other compounds are not observed, which proves the production of single-phase materials.

Micrographs of nickel ferrite samples (Fig. 2) indicate that the particles of the obtained material are uniform in morphology and size, have an octahedral shape and nanosize.

The method is confirmed by specific examples.

Example 1. Preparation of nickel ferrite powder from chloride solutions of nickel and iron (III) at a firing temperature of 650°C

Prepare the reaction solution from a mixture of 25 ml of 0.4 M NiCl solution₂6H₂O (2.38 g) and 25 ml 0.8 M FeCl₃6H₂O (5.41 g). The initial salts are dissolved in a 10% solution of dextran 40. A weighed portion of anion exchanger AB-17-8 weighing 86 g (SOE 1.4) is added to the resulting mixture.

The mixture is stirred on a shaker at a speed of 120 min.^-oneat 60°C for 1.5 hours. Next, the anion exchanger is separated from the precipitate and solution by passing the mixture through a sieve with a hole diameter of 0.16 mm. To separate the precipitate from the solution filtered under vacuum. The resulting precipitate is dried in an oven at a temperature of 80°C for 2 hours. The precipitate is fired at a temperature of 650°C for 3 hours. The product yield is 98%.

According to the elemental analysis data, the precipitate does not contain chloride ions. According to the atomic absorption analysis of the precipitate, the molar ratio of Ni ²⁺ /Fe ³⁺ is 0.5, which corresponds exactly to the stoichiometry of the final product. According to XRD data (Fig. 1), the target product is a nickel ferrite monophase, its size, calculated by the Debye-Scherrer formula, is 16.4±0.2 nm. According to transmission microscopy (Fig. 2), the product particles have an octahedral shape and a size of 23.5±1.0 nm.

In FIG. Figure 3 shows the dependence of the magnetization of the sample on the magnitude of the applied magnetic field, measured at T = 4.2 K. The data obtained indicate that this sample has magnetic parameters corresponding to a bulk NiFe ₂ O ₄ sample.

Example 2. Preparation of nickel ferrite powder from solutions of nickel and iron (III) nitrates at a firing temperature of 650°C

The reaction solution is prepared from a mixture of 25 ml of a 0.4 M solution of Ni(NO ₃ ) ₂ ^. 6H ₂ O (2.91 g) and 25 ml of 0.8 M Fe(NO ₃ ) ₃ ^. 6H ₂ O (8.08 g). The initial salts are dissolved in a 10% solution of dextran 40.

A portion of the anion exchanger AB-17-8 weighing 86 g is brought into contact with the reaction solution. The system is stirred on a shaker at a speed of 120 min.^-oneat 60°C for 1.5 hours. Next, the anion exchanger is separated from the precipitate and solution by passing the mixture through a sieve with a hole diameter of 0.16 mm. To separate the precipitate from the solution filtered under vacuum. The resulting precipitate is dried at a temperature of 80°C in an oven for 2 hours and fired at a temperature of 650°C for 3 hours. Product yield - 95%.

According to the elemental analysis data, the precipitate does not contain impurities of nitrate ions. According to the atomic absorption analysis of the precipitate, the Ni ²⁺ /Fe ³⁺ molar ratio is 0.5, which corresponds exactly to the stoichiometry of the final product. XRF data are similar to those obtained in example 1 (Fig. 1), which confirms the presence of a nickel ferrite monophase with a particle size of 16.4±0.2 nm calculated according to the Debye-Scherrer formula.

The radiograph of the product obtained in example 2, its micrograph and the spectrum of magnetic circular dichroism are similar to those presented in the first example (Fig. 1-3).

Thus, the inventive method for obtaining nanosized nickel ferrite powder is simple and easy to use, does not require the use of aggressive environments, high pressures, additional purification steps and sediment washing. Thanks to this method, it was possible to improve the characteristics of ferrite powders by obtaining a single-phase finely dispersed nanosized product.

Claims (1)

A method for producing nanosized nickel ferrite powder, which includes preparing a reaction solution from a mixture of nickel and iron (III) salts taken in a molar ratio of 1:2, obtaining a precipitate in the form of a powder, separating it, drying and firing, characterized in that that the reaction solution is prepared by dissolving a mixture of salts of chlorides or nitrates of nickel and iron (III) in a 10% solution of dextran 40, obtaining a precipitate in the form of a powder is carried out by stirring the resulting reaction solution with a strongly basic gel anion exchanger AB-17-8 in hydroxyl form at a temperature of 60 °C for 1.5 h, then the mixture is filtered, and the precipitate is dried at 80°C for 2 h and calcined at 650°C for 3 h.

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