RU2538585C2 - Method of obtaining nanodisperse metal oxides - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to methods of obtaining nanodisperse powder-like metal oxides, namely oxides of 3-d metals (scandium, titanium, vanadium, chrome, manganese, iron, cobalt, nickel, copper, zinc), 4-e-metals (yttrium, zirconium), metals of the third group of main subgroup (aluminium, gallium, indium). Elaborated is method of obtaining nanodisperse powders of metal dioxides, which includes continuous interaction, in flow mode, of metal nitrates with carbamide in molar ratio 2 mol of nitrate groups of metal salt to 1 mol of carbamide, with reaction medium being subjected to exposure to microwave radiation.

EFFECT: invention makes it possible to obtain nanodisperse powders with grain size not more than 30 nm.

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Description

The invention relates to methods for producing metal oxides and, in particular, to methods for producing nanodispersed powdered metal oxides, namely 3d metal oxides (scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc), 4d -metals (yttrium, zirconium), metals of the third group of the main subgroup (aluminum, gallium, indium).

The main field of application of oxides of such metals is their use as starting materials in the preparation of various ceramic materials, powder coatings, catalysts, catalyst supports, additives in polymeric materials, magnetic powders, and biomedical materials. In particular, ceramic materials based on zirconium oxide have long been used in orthopedics for the manufacture of implants and prostheses.

The use of metal oxides in the nanodispersed state makes it possible to reduce the sintering temperature in the preparation of ceramic materials. The search for simple ways to synthesize nanosized crystals of metal oxides is an urgent task of preparative chemistry.

Several modern technologies for producing nanodispersed ceramic materials are known:

- grinding coarse oxide in planetary or ball mills (mechanochemical),

- plasma-chemical spraying of the source metal or its salts [RU 2071678, IPC C01G 25/02, 05/18/1994],

- chemical coprecipitation from solution [RU 2194028 C2, IPC C04B 35/486, 02.26.2001],

- hydrothermal synthesis [CN 1636932, IPC C01G 25/02, publ. 07/13/2005].

The disadvantages of the known methods include multi-stage processes, the need to use special equipment to maintain high pressure in the synthesis of the material, or to use other than the main precipitating reagent, other reagents added specifically to form a favorable oxide structure.

Known [A Novel Approach For Preparation Of Y2o3: Eu3_Nanoparticles By Microemulsion_ / Microwave Heating. Qi Pang a, b, Jianxin Shi a, b, *, Yu Liu b, Desong Xing a, b, Menglian Gong a, b, Ningsheng Xu aa State Key Laboratory of Optoelectronic Materials and Technologies, Materials Science And Engineering B 103 (2003 ) 57_ / 61 www.elsevier.com/locate/mseb] the use of europium oxide (III) -doped with yttrium oxide (Y2O3: Eu3), as a substitute for phosphorus, in optical displays and luminous screens. The synthesis of this material is carried out by the interaction of aqueous solutions of yttrium nitrate and europium nitrate with an aqueous solution of ammonia by reverse emulsification in Triton (Triton X-100), n-hexanol, cyclohexane and water. The particles thus obtained are treated with microwave radiation to be converted to nanocrystalline oxide Y ₂ O ₃ : Eu ₃ .

The known method [application EP 2377506, IPC: A61C 5/08; A61K 6/02, publ. 19.10 2011] obtaining a ceramic material, including:

(i) obtaining an aqueous solution containing salts of zirconium, cerium, aluminum and at least one additional metal;

(ii) adding a base to obtain a precipitate; and

(iii) drying and / or calcining the precipitate.

The material contains at least one additional metal. Suitable opposing ions include chlorides, oxychlorides, nitrates, oxalates, hydroxides and carbonates, with chlorides being preferred. Examples of suitable salts include ZrCl ₄ , CeCl ₃ , AlCl ₃ , ZnCl _s , MgCl ₃ , LaCl ₃ and ZrOCl ₂ . For the deposition, a nitrogen-containing base is preferably used, for example, aqueous ammonia at a concentration of 20-35 wt.%. The base is added to the aqueous salt solution dropwise with stirring until a pH of 7.5 to 10 is reached, before the precipitation of hydroxides. The precipitated hydroxide is dried at a temperature of 100-120 ° C for 12-48 hours, ground and calcined at a temperature of 500-900 ° C for 1-3 hours. This multi-deposition technology is accompanied by the parallel deposition of at least two different crystalline phases, namely, the zirconia phase stabilized by CeO ₂ and the aluminate phase, such as ZnAl ₂ O ₄ , in one process step.

The aluminate is selected from the group consisting of ZnAl ₂ O ₄ , MgAl ₂ O ₄ , LaAlO ₃ and LaMgAl _n O _i9 .

Also known [RF Patent 2058939; IPC ⁶ C01G 25/02; Publ .: 04/27/1996 - prototype] a method of producing a powder of zirconium dioxide for the manufacture of ceramics. Dioxide powder is obtained from solutions of zirconium oxy nitrate and ammonia, which are poured simultaneously into a buffer solution.

In the buffer, a pH value of 7-8.5 is constantly maintained. The process is carried out with stirring and ultra-sounding with an oscillation frequency of 22-44 kHz. For this purpose, use the dispersant UZDN-2T.

In the second version, a solution of zirconium and yttrium nitrates was used as the initial one. The precipitation of zirconium hydroxide stabilized by yttrium is carried out continuously (cascade of reactors) with ultrasound in the range of 15-70 kHz without heating at pH 7.5. Then carry out the drying, calcination and grinding of the dried product. The grinding time is 1 hour. The optimal range of the ultrasonic field is the frequency range 20-50 kHz.

Thus, the technical solution described above uses dehydration and calcination and, in addition, ultra-sounding during the deposition of hydroxide. This deposition is carried out at a frequency of sound vibrations from 20 to 50 kHz for at least 5 minutes, followed by grinding of the dried mass for 0.5-1.0 hours. In this way, a uniform powder is obtained, mainly with a particle size of 0.1-4.0 microns.

The application of an ultrasonic field to the deposition of hydroxide contributes to the enlargement of the oxide powder. The structural homogeneity of the zirconium hydroxide powder is achieved by grinding, therefore, the grinding step is usually available in technologies for producing ceramic materials.

A common disadvantage of the described methods is their multi-stage and the need for a long and energy-intensive grinding stage.

As follows from the description [RF Patent 2058939; IPC ⁶ C01G 25/02; Publ .: 27.04.1996], the technological line, on which the prototype method is carried out, includes feeding solutions of zirconium oxynitrate and ammonia simultaneously into a buffer solution. The interaction process is carried out continuously in a cascade of reactors with ultrasound in the range of 15-70 kHz without heating at pH 7.5. Then carry out the drying, calcination and grinding of the dried product. The device of this technological installation is rather cumbersome, because a cascade of reactors, apparatuses for the implementation of the stages of calcination and grinding of the product are used.

The objective of the present invention is to develop a simple, technologically advanced method for producing nanosized powders of metal oxides, in particular 3d metal oxides (scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc), 4d metals (yttrium, zirconium ), metals of the third group of the main subgroup (aluminum, gallium, indium) with a grain size of not more than 30 nm.

The essence of the invention lies in the fact that a method has been developed for producing nanosized powders of metal oxides from aqueous solutions of metal nitrates, which consists in the continuous interaction of metal nitrates with urea in a molar ratio of 1-2 mol of nitrate groups of a metal salt to 1 mol of urea, the reaction medium is exposed to microwave radiation.

The method is designed to produce 3d metal oxides (scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc), and / or 4d metals (yttrium, zirconium), and / or metals of the third group of the main subgroup (aluminum, gallium, indium), by the interaction of solutions of the corresponding nitrates with urea.

More interaction can be described by the equation:

ZrO (NO ₃ ) ₂ + NH ₂ CONH ₂ → ZrO ₂ + 2N ₂ O + СО ₂ + 2Н ₂ О

The equation calculates the required quantities of the starting reagents:

- zirconyl nitrate dihydrate ZrO (NO ₃ ) ₂ · 2H ₂ O

- urea CO (NH ₂ ) ₂

Urea is introduced into the initial aqueous solution of metal nitrates at a concentration of up to 70 g / l in a molar ratio of 1 mol of urea to 2 mol of nitrate groups of the metal salt.

The drawing shows a diagram for producing nanodispersed powders of metal oxides from aqueous solutions of metal nitrates by the present method, where:

pos. 1 - mixer;

pos. 2 - a chamber of electromagnetic radiation;

pos. 3 - camera receiving products.

The method is as follows:

A urea solution and a metal nitrate solution in a predetermined ratio are mixed in a mixer (item 1). The resulting mixture is fed into the chamber of electromagnetic radiation (item 2). Under the action of electromagnetic radiation, the components of the mixture interact with each other and form nanosized metal oxides. In the process of interaction of the reagents, pairs are also formed that condense and are removed from the chamber of electromagnetic radiation. Nanodispersed metal oxides are discharged into the product reception chamber (item 3).

EXAMPLES

Example 1

Use initial solutions of magnesium nitrate and urea in a molar ratio of 2 mol of nitrate groups to 1 mol of urea (item 1). The reagents are microwaved at a microwave power of 700 watts (item 2). The reagents are exposed to microwave radiation, resulting in the formation of nanosized magnesium oxide (item 3).

The obtained powder was studied by X-ray phase analysis on a DRON-3 diffractometer using CuKα radiation. The analysis showed that a single-phase preparation was obtained in which there were no reflexes of reflections of the starting materials. Scanning electron microscopy data showed the production of magnesium oxide powder with a crystal size of not more than 10 nm.

Example 2

The synthesis of magnesium oxide was carried out from an aqueous solution of magnesium nitrate at a ratio of 2 mol of nitrate groups to 1 mol of urea (item 1). The reagents were subjected to microwave processing in the reactor for 10 minutes at a microwave power of 800 W (pos. 2).

The obtained powder was studied by x-ray phase analysis on a DRON-3 diffractometer using CuKα radiation (item 3). The analysis showed that a single-phase preparation was obtained in which there were no reflexes of reflections of the starting materials. Scanning electron microscopy data showed the production of magnesium oxide powder with a crystal size of not more than 10 nm.

Example 3

The synthesis of zinc oxide was carried out from the initial aqueous solutions of zinc nitrate in the ratio of nitrate groups: urea 2: 1 (item 1). The reagents are microwaved in the reactor for 20 minutes at a microwave output of 700 watts (item 2).

The resulting powder was studied by X-ray phase analysis on a DRON-3 diffractometer using CuKα radiation (item 3). The analysis showed that a single-phase preparation was obtained - zinc oxide, in which there were no reflexes of reflections of the starting materials. Scanning electron microscopy data showed a powder with a crystal size of not more than 10 nm.

Example 4

The synthesis of zinc oxide was carried out from a solution of zinc nitrate in the ratio of 0.2 mol of nitrate groups to 0.1 mol of urea in 400 ml of distilled water (item 1). The method is carried out as described above, but the microwave treatment was carried out for 15 minutes at a microwave power in the oven of 800 watts (item 2).

The obtained powder was studied by x-ray phase analysis on a DRON-3 diffractometer using CuKα radiation (item 3). The analysis showed that a single-phase preparation was obtained in which there were no reflexes of reflections of the starting materials. Scanning electron microscopy data showed the preparation of a powder with a crystal size of not more than 20 nm.

Example 5

The synthesis of zirconium oxide was carried out from the initial aqueous solutions of zirconium nitrate in the ratio of 0.02 mol of nitrate groups to 0.01 mol of urea in 200 ml of distilled water (item 1). The reagents were microwaved in the oven for 20 minutes at a microwave output of 800 watts (item 2).

The obtained powder was studied by x-ray phase analysis on a DRON-3 diffractometer using CuKα radiation (item 3). The analysis showed that a single-phase preparation was obtained in which there were no reflexes of reflections of the starting materials. Scanning electron microscopy data showed a powder with a crystal size of not more than 10 nm.

The complete solubility of the starting compounds and the high speed of the process lead to the production of zirconium dioxide in the nanodispersed state.

It was found that microwave treatment of a solution of zirconyl nitrate, which also contains carbamide as a nitrate reducing agent, made it possible to obtain a dry zirconium oxide powder after evaporating all the water. According to X-ray Phase Analysis (XRD), the powder is a crystal with a cubic zirconium oxide structure.

Scanning electron microscopy confirms the small size of the crystals. The zirconium oxide powder is mainly flat crystals, in which the thickness is much less than the length and width. Moreover, the thickness is not more than 10 nm, that is, the dimensions are in the nano-region.

Example 6

The synthesis of copper oxide was carried out from initial aqueous solutions of copper nitrate in the ratio of 0.02 mol of nitrate groups to 0.01 mol of urea in 200 ml of distilled water (item 1). The process is conducted as described above. Microwave processing is carried out for 20 minutes at a microwave power of 700 watts (item 2).

The obtained powder was studied by x-ray phase analysis on a DRON-3 diffractometer using CuKα radiation (item 3). The analysis showed that a single-phase preparation was obtained in which there were no reflexes of reflections of the starting materials. Scanning electron microscopy data showed a powder with a crystal size of not more than 5 nm.

Example 7

The synthesis of nickel oxide was carried out from initial aqueous solutions of nickel nitrate in the ratio of 0.02 mol of nitrate groups to 0.01 mol in distilled water (item 1). The reagents were microwaved for 10 minutes at a microwave output of 1200 watts (item 2).

The obtained powder was studied by x-ray phase analysis on a DRON-3 diffractometer using CuKα radiation (item 3). The analysis showed that a single-phase preparation was obtained in which there were no reflexes of reflections of the starting materials. Scanning electron microscopy data showed a powder with a crystal size of not more than 10 nm.

Example 8

As described above, alumina was synthesized from initial aqueous solutions of aluminum nitrate in the ratio of 0.02 mol of nitrate groups of aluminum nitrate to 0.01 mol of urea (item 1). The reagents were subjected to microwave processing for 10 minutes at a microwave power of 900 watts (item 2).

The obtained powder was studied by x-ray phase analysis on a DRON-3 diffractometer using CuKα radiation (item 3). The analysis showed that a single-phase preparation was obtained in which there were no reflexes of reflections of the starting materials. Scanning electron microscopy data showed the production of a powder with crystal sizes of aluminum oxide of not more than 10 nm.

Example 9

As described above, yttrium oxide was synthesized from solutions containing yttrium nitrate and urea in the ratio of 0.02 mol of yttrium nitrate groups to 0.01 mol of urea in 200 ml of distilled water (item 1). The reagents were microwaved in the oven for 20 minutes at a microwave output of 800 watts (item 2).

The obtained powder was studied by x-ray phase analysis on a DRON-3 diffractometer using CuKα radiation (item 3). The analysis showed that a single-phase preparation was obtained in which there were no reflexes of reflections of the starting materials. Scanning electron microscopy data showed a powder with a crystal size of not more than 10 nm.

Example 10

As described above, gallium oxide was synthesized from solutions containing gallium nitrate and urea in the ratio of 0.02 mol of gallium nitrate groups and 0.01 mol of urea (item 1). The reagents were microwaved in the oven for 15 minutes at a microwave output of 800 watts (item 2).

The obtained powder was studied by x-ray phase analysis on a DRON-3 diffractometer using CuKα radiation (item 3). The analysis showed that a single-phase preparation was obtained in which there were no reflexes of reflections of the starting materials. Scanning electron microscopy data showed a powder with a crystal size of not more than 10 nm.

An essential distinguishing feature is a new method for producing nanosized metal oxides, which provides for the introduction of urea metals into the nitrate solution in the prescribed ratio, as well as heat treatment of the initial solutions of nitrates in the microwave. The determining factors for obtaining such an ultrafine material is to conduct heat treatment in one stage under the action of microwave radiation.

Thus, the problem faced by the authors of this invention was solved - a simple, technologically advanced method for producing nanodispersed powders of 3d-metal oxides (scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc), 4d-metals was developed (yttrium, zirconium), metals of the third group of the main subgroup (aluminum, gallium, indium) with a grain size of 10 nm.

Claims (1)

A method of producing nanosized metal oxides from aqueous solutions of metal nitrates, which consists in the interaction of metal nitrates with urea in a molar ratio of 2 mol of nitrate groups of a metal salt to 1 mol of urea, while the reaction medium is exposed to microwave radiation.