RU2514258C1 - Method of production of superparamagnetic nickel particles and superparamagnetic powder composition - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed method comprises mixing of nickel compounds and poluolyc alcohol, heating of obtained mix, cooling it and centrifugation, flushing and drying of produced precipitate. Nickel compounds and poluolyc alcohol are taken at the ratio of 1-2 mmol/mol. Additionally alkali is introduced at the ratio of 2-3 mol to nickel mol and surfactant in amount of 10-30 mmol to nickel mol. Mix is heated in stepwise manner: First, it is heated from room temperature to 120°C at the rate of 10°C/min, then, from 120 to 190°C at the rate of 3.5°C/min. Thereafter, said mix is held for at least 10 minutes and cooled with the help of frozen distilled water. Multicomponent suspension after cooling is subjected to centrifugation, flushed and dried in air.

EFFECT: higher catalytic activity and safety, non-polluting process.

8 cl, 3 dwg, 22 ex

Description

The invention relates to the field of chemical nanotechnology, in particular to a technology for the production of nickel nanoparticles, which in modern conditions have a wide scope of application as, for example, nanocoatings in microelectronics, cooling components of coolants in nuclear energy, catalytic processes of different purposes, as well as in biomedicine and other branches of technology and production.

The extremely wide and diverse scope of nickel nanoparticles in modern technologies is due to the specific chemical nature of the heavy 3d element having 10 valence electrons, which leads to ferromagnetism and a combination of the relative chemical stability of the metal state with the simultaneous ability to form compounds with various oxidation states and complex compounds.

A known method of producing nickel nanoparticles with a catalytic effect as components of catalysts for the production of norbornene [1], which nickel nanoparticles are obtained directly during the first stage of heating the reaction mixture, and then, after the completion of the hydrogenation reaction, filtering the precipitate consisting of nickel. In the known method, the sizes of the resulting nickel particles are not indicated. At the same time, the presence of a precipitate in the method of filtering the obtained precipitate suggests that the obtained particles are quite large in size, on the order of tenth microns or microns, which indicates a small specific surface area of the nanoparticles obtained in this way and their insufficient catalytic activity.

A known method of producing nickel nanoparticles and their use as catalyst components for carbon dioxide conversion of methane or natural gas with the formation of synthesis gas [2]. Nickel nanoparticles obtained on the surface of a catalyst obtained in a known manner have insufficient activity due to their inevitable sintering at a temperature of catalyst synthesis of 900 ° C. At the same time, it is reported that when using nickel as an active component of a complex catalyst, the specific surface area of the catalyst, calculated as nickel, should be in the range of 150-250 m ² / g, i.e. the active component of the composition is nanometer in size.

A known method of producing nickel nanoparticles and their use as catalyst components for the production of aniline [3] and its derivatives in the presence of metal nanoparticles having variable valency, including nickel nanoparticles, which are obtained by the interaction of salt solutions with hydrazine in the first (preliminary) stages of the chemical target process of nitrobenzene reduction. However, nanoparticles of sufficiently large sizes are obtained in a known manner, which reduces their catalytic activity and, in addition, leads to an increased consumption of hydrazine.

There is a method of producing nickel nanoparticles by reduction of the original nickel hydroxide with hydrogen [4], however, nickel nanoparticles obtained in this way are quite large, on the order of tens of nanometers, which significantly limits their scope. In addition, the technology of the production itself has an increased danger for service personnel and also pollutes the environment, which makes it environmentally unclean.

A well-known method for producing nickel particles by reduction of nickel compounds with hydrazine hydrate belongs to the same environmentally unclean method and dangerous for staff [3], however, such production is associated with the use of a highly toxic chemical reducing agent.

A known method of producing metal particles [5], the closest to the claimed object of the invention is a method. In the known method, the starting compounds for the synthesis are oxides, hydroxides and metal salts, and the reducing agent is polybasic alcohols (polyols); the resulting suspension of the starting components in polyols is heated to a temperature of more than 85 ° C degrees.

The disadvantages of this method are to obtain sufficiently large metal particles, which reduces their catalytic activity and increases aggregative instability, thereby narrowing the scope of possible applications. In addition, a significant disadvantage of this method also relates to the complexity of the technology, the increased danger of production and environmental pollution, worsening the environment.

A known composite of nickel nanoparticles with a diameter of 10 nm [6-7] and liquid sodium, which is used as a liquid cooling medium in the form of coolants in a nuclear fast neutron reactor. This composition reduces the toxicity of the coolant and its reactivity, increases the hydraulic resistance and thermal conductivity. However, the nanoparticles included in such a composition are not small enough, which leads only to a slight increase in hydraulic resistance and an incomplete decrease in the toxicity of the coolant.

Known composition, which is a colloidal solution based on glycerol and nickel nanoparticles, which is used for laser deposition of metal nanolayers in the manufacture of electronic equipment and quantum electronics [8]. The disadvantage of such a colloidal solution is its aggregative instability, due to the large particle size and the absence of surfactants attached to the surface of the particles.

A known composition of metal particles closest to the claimed second object of the invention, composition [9], which consists of nickel nanoparticles coated to protect them from aggressive environments and to impart aggregative stability to one or more surfactants - amine oxide with groups of composition R ₁ R ₂ R ₃ NO, where R ₁ is unsubstituted alkyl (C ₁₄ to C ₃₀ ), and R ₂ and R ₃ are the same or unsubstituted C ₁ -C ₆ alkyl. The particles coated with them have a linear size of 50 nm or less, and the mass of the metal core is substantially less than half the mass of the obtained composite particles. The synthesis of such particles is multistage and very complicated, requires the use of powerful reducing agents, and coated particles have aggregative stability only in a liquid medium.

The claimed invention is free from these disadvantages.

The technical result of the claimed invention is to obtain nickel nanoparticles with higher catalytic activity, expanding the scope of their application, simplifying the method of their preparation, as well as reducing production safety and improving the environment.

A method for producing superparamagnetic nickel particles involves mixing nickel compounds and polyol alcohol, heating the resulting mixture, cooling and centrifuging it, washing and drying the precipitate obtained. The nickel and polyol alcohol compounds are taken between themselves in a ratio of 1 to 2 mmol / mol, alkali is additionally added to the mixture in a ratio of 2 to 3 mol to mol of nickel and a surfactant from 10 to 30 mmol to mol of nickel. The mixture is heated stepwise: first from room temperature to 120 ° C at a speed of 10 ° C / min, then from 120 to 190 ° C at a speed of 3.5 ° C / min and the mixture is kept for at least 10 minutes, after which cooling the mixture using frozen distilled water. The multicomponent suspension obtained after cooling is centrifuged, washed and dried in air.

As a surfactant, acids from the series can be used: phosphonic acid (hydroxyethylidene diphosphonic and nitrilotrimethylphosphonic acid), polycarboxylic acid (citric, or tartaric, or malic acid), limiting acids (valerianic, or lauric, or stearic).

Superparamagnetic powder composition based on superparamagnetic nickel particles with a linear size of 5-10 nm and a specific magnetization of 0.5 A · m ² / kg, obtained by the method disclosed above, contains components in the following ratio, wt.%:

nickel metal 54.7 surfactant 0.8 polyol oligomers 39.5 adsorbed solvents 5.

The specified technical result is achieved due to the fact that the use of surfactant and the choice of heating and cooling regimes provide the formation of weakly interacting stable superparamagnetic particles with a linear size of less than 10 nm, covered with a protective passivating shell of various thicknesses.

On the basis of St. Petersburg State University was tested the proposed method for producing nickel nanoparticles and compositions based on them.

The obtained results of laboratory studies are illustrated in Figs. 1-3 and specific examples (1-8) carried out in real time.

Figure 1 presents an electron micrograph of the product obtained by the prototype (example 1). The product consists of crystals with facets larger than 100 nm and semi-amorphous aggregates.

Figure 2 presents an electron micrograph of the powder obtained in example 2. The average particle size is 14 nm. Aggregates arise only as a result of drying of the droplets of the suspension on the substrate during the shooting. Particles in the aggregate are well distinguishable.

Figure 3 presents the derivatogram of the powder obtained according to example 2. The survey was carried out in an argon stream on a NETZSHC STA 429 CD derivatograph in the temperature range from 20 to 1000 ° C, at a heating rate of 20 ° C / min. Losses of bound water and adsorbed solvents at temperatures below 270 ° C are 0.54 and 4.78% of the initial mass. Losses due to two-stage removal of polyethylene glycol oligomers from the surface of the nanoparticles are 41.90%. A further increase in temperature does not lead to a decrease in the mass of the powder.

Example 1

Laboratory studies were conducted to verify the results of the synthesis of the prototype.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate are poured into 500 ml of ethylene glycol, heated to a temperature of 198 ° C, incubated for two hours, cooled to room temperature, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air atmosphere at 50 ° C. According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the particle size is in the range of 20-300 nm, the powder is not monodisperse. The saturation magnetization in a field of 10 kOe is 13 A · m ² / kg.

Figure 1 presents an electron micrograph of a product obtained by the prototype, which consists of crystals with a facet size of more than 100 nm and semi-amorphous aggregates.

Example 2

Laboratory studies were carried out to confirm the advantages of the heating-cooling mode proposed in the application.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate are added to 500 ml of ethylene glycol, heated to 120 ° C for 10 minutes, heated from 120 to 190 ° C for 20 minutes, incubated for 45 minutes at 190 ° C, cooled to room temperature temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the particle size is 14 nm, the powder is monodisperse. The saturation magnetization in a field of 10 kOe is 1.1 A · m ² / kg.

Figure 2 presents an electron micrograph of the powder. The observed particles are close in size. The average particle size is 14 nm. Aggregates arise only as a result of drying of the droplets of the suspension on the substrate during the shooting. Particles in the aggregate are well distinguishable.

Figure 3 presents the derivatogram of the obtained powder. The survey was carried out in an argon flow on a NETZSHC STA 429 CD derivatograph in the temperature range from 20 to 1000 ° C, at a heating rate of 20 ° C / min. The solid curve represents the data of thermogravimetric analysis, the discontinuous curve represents the differential thermogravimetric analysis. Losses of bound water and adsorbed solvents at temperatures below 270 ° C are 0.54 and 4.78% of the initial mass. Losses due to two-stage removal of polyethylene glycol oligomers from the surface of the nanoparticles in the region of 270-370 ° C are 41.90%. A further increase in temperature does not lead to a decrease in the mass of the powder. Figure 3 demonstrates the ability to completely remove the polyol as one shell from particles at temperatures below 400 ° C in an inert atmosphere.

Example 3

Laboratory studies were conducted to confirm the benefits of sharing the proposed heating-cooling and surfactant (HEDP) regimen and to confirm the stability of the powder properties during storage.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate, 0.0295 g of hydroxyethylidene diphosphonic acid (HEDP) are added to 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 20 minutes, kept for 10 minutes at a temperature of 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the particle size is 10 nm, the powder is monodisperse. The saturation magnetization in a field of 10 kOe is 0.50 A · m ² / kg.

After storage in air for 60 days, the powder showed a constant specific magnetization, i.e. not subjected to oxidation.

Example 4

Laboratory studies were conducted to confirm the benefits of sharing the proposed heating-cooling regimen with the nitrilotrimethylphosphonic acid (NTP) surfactant.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0642 g of NTP are added to 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 20 minutes, incubated for 10 minutes at a temperature of 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C. The amounts of reagents used correspond to the following ratios: nickel / ethylene glycol 1.60 mmol / mol, alkali / nickel 2.49 mol / mol, NTF / nickel 15 mmol / mol.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the particle size is 7 nm, the powder is monodisperse. The saturation magnetization in a field of 10 kOe is 0.20 A · m ² / kg.

After storage in air for 60 days, the powder showed a constant specific magnetization, i.e. not subjected to oxidation.

Example 5

Laboratory studies were conducted to confirm the benefits of sharing the proposed heating-cooling regimen with tartaric acid surfactant, which is hydroxypolycarboxylic acid.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0322 g of tartaric acid are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 20 minutes, incubated for 10 minutes at 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C . The initial tartaric acid / nickel ratio is 15 mmol / mol.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the particle size is 5-10 nm, the powder is monodisperse. The saturation magnetization in a field of 10 kOe is 0.50 A · m ² / kg. According to chemical analysis, the powder contains: nickel - 54.7%, surfactant - 0.8%, polyol oligomers - 39.5%, adsorbed solvents - 5%.

After storage in air for 60 days, the powder showed a constant specific magnetization, i.e. not subjected to oxidation.

Example 6

Laboratory studies were conducted to confirm the benefits of sharing the proposed heating-cooling regimen with a surfactant - malic acid, which is hydroxypolycarboxylic acid.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0480 g of malic acid are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 20 minutes, incubated for 10 minutes at 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C . The initial malic acid / nickel ratio is 25 mmol / mol.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the average particle size is 9 nm, the powder is monodisperse. The saturation magnetization in a field of 10 kOe is 0.35 A · m ² / kg.

Example 7

Laboratory studies were conducted to confirm the benefits of using valerianic acid as a surfactant.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate are poured into 500 ml of ethylene glycol, 1.5 ml of a 1% solution of valerianic acid in ethanol are poured, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 180 ° C for 20 minutes, kept for 45 minutes at a temperature of 180 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the particle size is 3 nm, the powder is monodisperse. According to the combination of chemical, derivatographic, and IR spectral data, the composition of the resulting composition is 60% metallic nickel, 0.76% valerianic acid, 39.24% ethylene glycol oligomers, and adsorbed solvents. The saturation magnetization in a field of 10 kOe is 0.50 A · m ² / kg.

Example 8

Laboratory studies have been conducted to confirm the benefits of using lauryl acid as surfactants.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate, 0.0286 g of lauric acid are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 20 minutes, heated from 120 to 190 ° C for 20 minutes, kept for 10 minutes at a temperature 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethanol, and dried in air at 50 ° C.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the particle size is 3 nm, the powder is monodisperse. The saturation magnetization in a field of 10 kOe is 0.35 A · m ² / kg.

Example 9

Laboratory studies have been conducted to confirm the benefits of using stearic acid as surfactants.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate, 0.041 g of stearic acid are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 60 minutes, heated from 120 to 190 ° C for 20 minutes, kept for 10 minutes at a temperature of 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethanol, and dried in air at 50 ° C.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the particle size is 24 nm, the powder is monodisperse. The saturation magnetization in a field of 10 kOe is 0.35 A · m ² / kg.

Example 10

Laboratory studies were conducted to confirm the benefits of using citric acid as surfactants.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate, 0.0824 g of citric acid are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 60 minutes, heated from 120 to 190 ° C for 20 minutes, kept for 10 minutes at a temperature 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethanol, and dried in air at 50 ° C.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the particle size is 10 nm, the powder is monodisperse. The saturation magnetization in a field of 10 kOe is 0.80 A · m ² / kg.

Example 11

Laboratory studies were carried out to verify the synthesis results with altered component ratios, namely, the ratios of nickel / ethylene glycol, alkali / nickel, surfactant / nickel by changing the amount of nickel salt.

1.428 g of sodium hydroxide and 0.5712 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0642 g of NTP are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 20 minutes, incubated for 10 minutes at 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C. The amounts of reagents correspond to the following ratios: nickel / ethylene glycol 0.257 mmol / mol, alkali / nickel 15.52 mol / mol, NTF / nickel 93.5 mmol / mol.

According to x-ray phase analysis, the product by phase composition is amorphous. After washing it is not possible to precipitate. The result is negative.

Example 12

Laboratory studies were carried out to verify the synthesis results with altered component ratios, namely, the ratios nickel / ethylene glycol, alkali / nickel, surfactant / nickel due to an increase in the amount of nickel salt.

1.428 g of sodium hydroxide and 8,000 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0642 g of NTP are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 20 minutes, incubated for 10 minutes at a temperature of 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C. The amounts of reagents correspond to the following ratios: nickel / ethylene glycol 3.59 mmol / mol, alkali / nickel 1.11 mol / mol, NTF / nickel 6.68 mmol / mol.

According to x-ray phase analysis, the product by phase composition is a mixture of nickel hydroxide, nickel oxide and metallic nickel, i.e. does not meet the purpose of the invention.

Example 13

Laboratory studies were carried out to verify the results of the synthesis with altered ratios of the starting components, namely, the alkali / nickel ratio, by reducing the amount of alkali. Other quantities of starting reagents and their ratios and heating modes are used the same as in example 3.1.

0.503 g of sodium hydroxide and 3.546 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0642 g of NTP are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 20 minutes, incubated for 10 minutes at a temperature of 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C. The amounts of reagents correspond to an alkali / nickel ratio of 0.877 mol / mol.

According to x-ray phase analysis, the product by phase composition is mainly a mixture of hydroxide and nickel oxide, i.e. does not meet the purpose of the invention.

Example 14

Laboratory studies were carried out to verify the results of synthesis with modified ratios of the starting components, namely, the alkali / nickel ratio, by increasing the amount of alkali. Other quantities of starting reagents and their ratios, as well as heating modes are used the same as in example 3.1.

4.282 g of sodium hydroxide and 3.546 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0642 g of NTP are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 20 minutes, incubated for 10 minutes at a temperature of 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C. The amount of reagents corresponds to an alkali / nickel ratio of 7.47 mol / mol.

The product after centrifugation is a viscous mass that cannot be washed in water and alcohol due to the increased content of ethylene glycol oligomers, i.e. the product does not meet the purpose of the invention.

Example 15

Laboratory studies were carried out to verify the results of synthesis with modified ratios of the starting components, namely, the surfactant / nickel ratio, by reducing the amount of surfactant. Other quantities of starting reagents and their ratios and heating modes are used the same as in example 3.1.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0096 g of malic acid are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 20 minutes, incubated for 10 minutes at 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C . The initial malic acid / nickel ratio is 5 mmol / mol.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the powder is polydisperse, contains a fraction of particles with a size of 120 nm. The saturation magnetization in a field of 10 kOe is 3.5 A · m ² / kg.

Example 16

Laboratory studies were carried out to verify the results of the synthesis with altered ratios of the starting components, namely, the surfactant / nickel ratio, by increasing the amount of surfactant. Other quantities of starting reagents and their ratios, as well as heating modes are used the same as in example 3.1.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.214 g of NTP are added to 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 20 minutes, incubated for 10 minutes at a temperature of 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethanol and dried in air at 50 ° C. The ratio of NTF / Nickel is 50 mmol / mol.

According to x-ray phase analysis, the product according to the phase composition is a highly dispersed metallic nickel. According to transmission electron microscopy, the particles are highly aggregated, connected by organic polymers. The saturation magnetization in a field of 10 kOe is 0.07 A · m ² / kg. The product is poorly washed due to the high content of oligomers. After drying the product according to chemical analysis, the nickel content in the composition is only 17.3%, which does not meet the purpose of the invention.

Example 17

Laboratory studies were carried out to confirm the possibility of removing polyol shell particles from particles while maintaining chemical stability due to the presence of surfactants.

The powder obtained in example 2 was calcined in an inert atmosphere of helium at 350 ° C for 30 minutes and cooled in a helium stream to 50 ° C. According to transmission electron microscopy, the particle size is in the range of 30-70 nm. The saturation magnetization in a field of 10 kOe is 35.70 A · m ² / kg. The powder was stored in air, retained magnetic properties when tested after 180 days.

Example 18

Laboratory studies were conducted to confirm the optimality of the selected mode of heating the mixture of the starting components. The number and proportions of the components are the same as in example 3.1, a longer warm-up from room temperature to 120 ° C was applied.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0642 g of NTP are added to 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 60 minutes, heated from 120 to 190 ° C for 20 minutes, incubated for 10 minutes at a temperature of 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C. The amounts of reagents correspond to the following ratios: nickel / ethylene glycol 1.60 mmol / mol, alkali / nickel 2.49 mol / mol, NTF / nickel 15 mmol / mol.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the polydisperse powder contains a fraction of 130 nm. This fraction of the powder is not superparamagnetic, the powder has a coercive force of 145 Oe, which is a negative result.

Example 19

Laboratory studies were conducted to confirm the optimality of the selected mode of heating the mixture of the starting components. The number and proportions of the components are the same as in example 3.1, faster heating from room temperature to 120 ° C is applied.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0642 g of NTP are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 4 minutes, which leads to local overheating of the liquid phase on the walls of the vessel, heated from 120 to 190 ° C for 20 minutes, kept for 10 minutes at 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C. The amounts of reagents correspond to the following ratios: nickel / ethylene glycol 1.60 mmol / mol, alkali / nickel 2.49 mol / mol, NTF / nickel 15 mmol / mol.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the polydisperse powder contains a fraction of 140 nm. This fraction of the powder is not superparamagnetic, the powder has a coercive force of 140 Oe, which is a negative result.

Example 20

Laboratory studies were conducted to confirm the optimality of the selected mode of heating the mixture of the starting components. The number and ratios of components are the same as in example 3.1, delayed heating was applied from a temperature of 120 ° C to a temperature of 190 ° C.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0642 g of NTP are added to 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 60 minutes, incubated for 10 minutes at a temperature of 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C. The amounts of reagents correspond to the following ratios: nickel / ethylene glycol 1.60 mmol / mol, alkali / nickel 2.49 mol / mol, NTF / nickel 15 mmol / mol.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the powder is polydisperse. A large fraction of the powder (about 150 nm) is not superparamagnetic, so the powder has a coercive force of 128 Oe, which is a negative result.

Example 21

Laboratory studies were conducted to confirm the optimality of the selected mode of heating the mixture of the starting components. The number and ratios of components are the same as in example 3.1, faster heating was applied from a temperature of 120 ° C to a temperature of 190 ° C.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.0642 g of NTP are added to 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C for 7 minutes, incubated for 10 minutes at a temperature of 190 ° C, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethyl alcohol and dried in air at 50 ° C. The amounts of reagents correspond to the following ratios: nickel / ethylene glycol 1.60 mmol / mol, alkali / nickel 2.49 mol / mol, NTF / nickel 15 mmol / mol.

According to x-ray phase analysis, the product according to the phase composition is a metallic nickel. According to transmission electron microscopy, the powder is polydisperse due to local overheating of the solution. A large fraction of the powder (100-150 nm) is not superparamagnetic, therefore, the powder has a coercive force of 135 Oe, which is a confirmation of a negative result.

Example 22

Laboratory studies were conducted to confirm the optimality of the selected mode of heating the mixture of the starting components. The number and ratio of components are the same as in example 3.2. The difference between the example in the absence of a 10 minute stay of the powder at a temperature of 190 ° C after it is reached.

1.428 g of sodium hydroxide and 3.561 g of nickel acetate Ni (CH ₃ COO) ₂ · 4H ₂ O, 0.322 g of tartaric acid are poured into 500 ml of ethylene glycol, heated to a temperature of 120 ° C for 10 minutes, heated from 120 to 190 ° C in for 20 minutes, cooled to room temperature using frozen distilled water, then isolated by centrifugation, washed once in distilled water and twice in ethanol, and dried in air at 50 ° C.

According to x-ray phase analysis, the product by phase composition is a mixture of nickel and nickel hydroxide, which is a confirmation of a negative result.

As the results of numerous approbations show, the claimed method leads to the production of such nickel nanoparticles coated with a protective shell consisting of a surfactant and polyol oligomers, whose unique properties make it possible to widely use the compositions obtained on their basis:

in medicine in the diagnosis, magnetic separation and therapy of tumors due to their small size and superparamagnetism;

electronics as a component for applying thin contact coatings, due to the possibility of obtaining stable colloidal suspensions of high concentration on the basis of particles;

in catalytic systems for the hydrogenation of hydrocarbons and their derivatives in gas and liquid media due to the ability to remove the polyol as one shell while maintaining the stability of the particles and their nanoscale;

as a component for coolants in nuclear reactors, due to their small size and the possibility of surface binding to an alkali metal atom;

as magnetic marks on banknotes and documents that are invisible at room temperature and exhibit ferromagnetism when the temperature is lowered due to the super-magnetic characteristics they exhibit, which are stable for a long time.

List of references

1. Patent RU 2456262 C1.

2. Patent RU 2453366 C1.

3. Patent RU 2433116 C1.

4. Patent RU 2170647 C2.

5. Patent US 4,539,041 (prototype for the method).

6. Patent RU 2326921 C2.

7. Patent RU 2291889 C2.

8. Patent RU 2433948 C1.

9. EP 2409762 A1 (prototype for the composition).

Claims (8)

1. A method for producing superparamagnetic nickel particles, comprising mixing nickel compounds and polyol alcohol and subsequent heating of the resulting mixture, cooling and centrifuging, washing and drying the precipitate obtained, characterized in that the nickel and polyol alcohol compounds are taken from each other in a ratio of 1 to 2 mmol / mol, alkali is additionally introduced into the mixture in a ratio of from 2 to 3 mol to mol of nickel and surfactant from 10 to 30 mmol to mol of nickel, the mixture is heated stepwise: first from room temperature to 120 ° C at a rate of 10 ° C / min, then from 120 to 190 ° C at a rate of 3.5 ° C / min and the mixture is kept for at least 10 minutes, after which the mixture is cooled using frozen distilled water, the multicomponent suspension obtained after cooling centrifuged, washed and dried in air. 2. The method according to claim 1, characterized in that phosphonic acid is used as a surfactant. 3. The method according to claim 1, characterized in that polycarboxylic acid is used as a surfactant. 4. The method according to claim 2, characterized in that oxyethylidene diphosphonic and nitrilotrimethylphosphonic acid are used as phosphonic acid. 5. The method according to claim 3, characterized in that citric or tartaric or malic acid is used as the polycarboxylic acid. 6. The method according to claim 1, characterized in that the limit acid is used as a surfactant. 7. The method according to claim 6, characterized in that valerianic, or lauryl, or stearic are used as limiting acids. 8. Superparamagnetic nickel particles obtained by the method according to claim 1, characterized in that they have a linear size of 5-10 nm, a specific magnetization of 0.5 A · m ² / kg and the following composition, wt.%:
nickel metal 54.7 surfactant 0.8 polyol oligomers 39.5 adsorbed solvents 5

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