Method of obtaining nanotubular structures of oxides of vanadium or chrome subgroup (versions)

FIELD: chemistry, technological processes.

SUBSTANCE: method of obtaining nanotubular structures includes mixing of oxygen-containing organic compound - oxalic acid hydrate with vanadium oxide gel or oxygen-containing compound of respective metal. As oxygen-containing compound of respective metal, peroxide molybdenum or tungsten oxides are used.

EFFECT: reduction of interlayer distance in structure of nanotubular structures of said oxides due to absence in structure of extraneous radicals of organic compounds.

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The invention relates to methods for allotropic forms oxides subgroups of vanadium or chromium, which can be used as magnetic materials for the creation of spintronic devices, field-effect transistors, chemical current sources, photochromic and catalytically active materials.

A method of obtaining nanotubular structures consisting of vanadium mixed valence (U.S. patent No. 6210800, Ál. D01F 9/00, 2001). In the known method, the vanadium oxide-triisopropoxide in the number 15,74 mmol add to 7.87 mmol of hexadecylamine in an argon atmosphere and stirred for 1 hour adding 5 ml of absolute ethanol. The resulting solution hydrolyzing, resulting orange precipitate, which is aging with stirring for 1 day. This reaction mixture is heated in the autoclave 1 day up to 80°the next day to 100° and within 7 days up to 180°C. Receive a black product, which is filtered off, washed with water, ethanol, ether and dried in air. Receive nanotubes with open and closed ends of a length of up to 2 microns and a diameter of 15-100 nm. Empirical formula nanotubes VO_2,4(C₁₆H₃₃NH₂)_0,34.

The disadvantages of this method are multi-stage, duration of the process, as well as a high content of amines in the floor structure is obtained nanotubes, what causes the multiple layers of their structure and large interlayer distance.

A method of obtaining nanotubular structures of molybdenum trioxide, comprising heating the IR-radiation of molybdenum foil in a moderate vacuum on tantalum substrate at 950-1000°C for 1 hour. On tantalum substrate film is formed of a quasilinear tube length 5-8 μm, an outer diameter of 50-300 nm and inner - 20-150 nm (Li Y., Bando Y. "Quasi-aligned MoO₃nanotubes grown on The substrate", Chem. Phys. Lett., 2002, v.364, p.484-488).

The disadvantages of this process are the complexity of the process caused by the use of IR-radiation, high temperature synthesis, and the formation of the nanotubes in the form of a film, making it difficult to separate them from the tantalum substrate.

Closest to the proposed technical solution is the method of obtaining nanotubular structures of vanadium oxide (patent RF №2240980, Ál. 01G 31/02, 2004). In the known method the gel of vanadium oxide (V) and an aqueous solution of polyvinyl alcohol in a molar ratio of 1:1 is stirred for at least 30 minutes the reaction mixture is placed in an autoclave, heated to 180°and at this temperature, incubated for 3 days. After that, the autoclave is cooled to room temperature, the obtained product is filtered, washed with water and dried in vacuum at 80°C for 3 hours. Filed phase analysis of the obtained dry product has the structure of orthorhombic oxide of vanadium (V) with empiricheskoi formula VO _2,35(C₂H₃)_{of 0.2}and according to electron microscopic studies consists of tubes with closed and open ends of the diameter of 30-150 nm and length of several micrometers, stuck in the beam.

The disadvantage of this method is the low quality of the product due to the high content of vinyl radicals in the structure of the nanotubes, resulting in multiple layers of the structure and a large interlayer distance (13,9±0,1Å).

Thus, the authors was to develop a method of obtaining nanotubular structures of the oxides of vanadium or molybdenum or tungsten, ensuring a higher quality final product.

The technical result of the proposed solutions is to reduce the interlayer distances in the structure nanotubular structures of these oxides due to the absence in the structure of foreign radicals of organic compounds.

The problem is solved in a method of producing nanotubular structures of vanadium oxides, including mixed gel of vanadium oxide and oxygen-containing organic compounds, subsequent heating of the mixture in the autoclave, filtration, washing and drying the obtained precipitate, in which the oxygen-containing organic compounds using a hydrate of oxalic acid at a molar ratio of Vⁿ⁺: hydrate is avaliou acid, equal to 1:(0,33÷1,50).

The goal is also solved in the method of obtaining nanotubular structures of the oxides of molybdenum or tungsten, comprising a mixture of aquacomplex suitable metal and oxygen-containing organic compounds, subsequent heating of the mixture in the autoclave, filtration, washing and drying the obtained precipitate, which as aquacomplex metal using an aqueous solution of paracomplex metal obtained by dissolving the powder of the corresponding metal in the hydrogen peroxide, as well as oxygen-containing organic compounds using a hydrate of oxalic acid at a molar ratio of Mⁿ⁺: hydrate oxalic acid, equal to 1:(0,33÷1,50).

At the present time of patent and technical literature is not a method of obtaining nanotubular structures of vanadium oxides, in which the composition of the reaction mixture using a hydrate of oxalic acid in certain molar ratio of the starting components, and a method of producing oxides of molybdenum or tungsten, in which the composition of the reaction mixture using paracomplex and hydrate oxalic acid in certain molar ratio of the starting components

The proposed method can be implemented as follows. Take the gel of vanadium oxide or an aqueous solution lane is cocomplex molybdenum or tungsten and add to it the hydrate of oxalic acid to obtain a molar ratio of M ⁿ⁺: H₂With₂About₄·2H₂O = 1:(0,33÷1,50), then stirred until a homogeneous consistency. The resulting reaction mixture is placed in an autoclave, heated to 180-200°and at this temperature, incubated 5-7 days. After that, the autoclave is cooled to room temperature, the obtained product is filtered, washed with ethanol and dried. According to the phase of analysis of the obtained dry product has a structure of the oxides of vanadium, or molybdenum, or tungsten, and according to electron microscopic studies is made from 100% nanotubular structures.

Use to obtain a reaction mixture of oxalic acid, you achieve odnofaznogo nanostructures with interlayer distance of less than 9 Åbecause in the resulting structure are absent radicals foreign organic compounds, such as vinyl radicals in the known method, specified as a prototype. The process in the proposed limits of the molar ratio of components allows to obtain a single-phase product, thus decreasing the molar ratio less than 1:0,33 or increase of more than 1:1,50, there is contamination of the obtained nanostructures extraneous impurities of oxides of the respective metal of a different valence.

The proposed method is illustrated by the following examples, the AMI.

Example 1. Take 30 ml of gel of vanadium oxide V₂O₅with the vanadium content of 0.15 mol/l and add to it to 0.19 g of the hydrate of oxalic acid (molar ratio V⁵⁺: H₂C₂About₄-2H₂O = 1:0,33), then stirred until a homogeneous consistency. The resulting reaction mixture is placed in an autoclave, heated to 190°and at this temperature, incubated for 6 days. After that, the autoclave is cooled to room temperature, the obtained product is filtered, washed with ethanol and dried in vacuum at 80°C for 3 hours. According to the phase of analysis and electron microscopic studies of the obtained dry product is almost 100% composed of nanotubes with an outer diameter of 50-60 nm, a length of 2-5 μm with the structure of the oxide V₃O₇·nH₂O. figure 1 shows the image of the nanotubes, which is obtained with an electron microscope.

Example 2. Take 30 ml of gel of vanadium oxide V₂O₅with the vanadium content of 0.15 mol/l and add to it 0,57 g of oxalic acid hydrate (molar ratio V⁵⁺: H₂C₂O₄·2H₂O = 1:1), then stirred until a homogeneous consistency. The resulting reaction mixture is placed in an autoclave, heated to 200°and at this temperature withstand 7 days. After that, the autoclave is cooled to room temperature the tours, the resulting product is filtered, washed with ethanol and dried in vacuum at 80°C for 3 hours. According to the phase of analysis and electron microscopic studies of the obtained dry product is almost 100% composed of nanotubes with an outer diameter of 50-60 nm, a length of 8 μm, with the structure of the oxide V₆O₁₃. Figure 2 shows an image of the nanotubes, which is obtained with an electron microscope.

Example 3. Take 30 ml of gel of vanadium oxide V₂O₅with the vanadium content of 0.15 mol/l and add to it of 0.85 g of the hydrate of oxalic acid (molar ratio V⁵⁺: H₂With₂About₄·2H₂O = 1:1,5), then stirred until a homogeneous consistency. The resulting reaction mixture is placed in an autoclave, heated to 200°and at this temperature withstand 7 days. After that, the autoclave is cooled to room temperature, the obtained product is filtered, washed with ethanol and dried in vacuum at 80°C for 3 hours. According to the phase of analysis and electron microscopic studies of the obtained dry product is almost 100% composed of nanotubes with an outer diameter of 2.8 nm, a length of 60 to 150 nm, the structure of the oxide VO₂(In). Figure 3 shows the image of the nanotubes, which is obtained with an electron microscope.

Example 4. Take 30 ml of an aqueous solution feather is of cocomplex of molybdenum from the molybdenum content of 0.17 mol/l and add 0.34 g of oxalic acid hydrate (molar ratio Mo ⁶⁺: H₂C₂About₄·2H₂O = 1:0.5), and then stirred until a homogeneous consistency. The resulting reaction mixture is placed in an autoclave, heated to 180°and at this temperature, allowed to stand 5 days. After that, the autoclave is cooled to room temperature, the obtained product is filtered, washed with ethanol and dried in vacuum at 80°C for 3 hours. According to the phase of analysis and electron microscopic studies of the obtained dry product is almost 100% composed of nanotubes with an outer diameter of 60-100 nm, a length of several microns to the structure of the oxide of Moo_3-δ·0,N₂O. figure 4 shows an image of the nanotubes, which is obtained with an electron microscope.

Example 5. Take 20 ml of an aqueous solution of paracomplex tungsten containing tungsten of 0.14 mol/l and add 0.51 g of oxalic acid hydrate (molar ratio W⁶⁺: H₂With₂About₄·2H₂O = 1:1,5), then stirred until a homogeneous consistency. The resulting reaction mixture is placed in an autoclave, heated to 190°and at this temperature withstand 7 days. After that, the autoclave is cooled to room temperature, the obtained product is filtered, washed with ethanol and dried in vacuum at 80°C for 3 hours. According to the phase analysis and electron microscopic studies of the obtained dry product is almost 100% composed of nanorods with an external diameter of 11-35 nm, length 64-160 nm, the structure of the oxide WO₃·0,N₂O. figure 5 shows the image of the nanorods, which is obtained with an electron microscope.

Thus, the authors propose a method of obtaining single-phase nanotubular structures of the oxides of vanadium or molybdenum, or tungsten that enhance the quality of the structure due to the absence of extraneous organic radicals and reduce consequently the interlayer distance. In addition, the method allows to extend the range of the resulting nanostructures. The work was supported by RFBR-GFEN of China (project No. 03-03-39009).

1. The method of obtaining nanotubular structures of vanadium oxides, including mixed gel of vanadium oxide and oxygen-containing organic compounds, subsequent heating of the mixture in the autoclave, filtration, washing and drying the obtained precipitate, characterized in that as the oxygen-containing organic compounds using a hydrate of oxalic acid at a molar ratio of Vⁿ⁺: oxalic acid hydrate is equal to 1:(0,33÷1,50).

2. The method of obtaining nanotubular structures of metal oxides, comprising a mixture of oxygen-containing compounds suitable metal with oxygen-containing organic compound, followed by heating the mixture in the autoclave, filtered, prom the internals and drying the obtained precipitate, characterized in that as the oxygen-containing compounds suitable metal use peroxide oxide of molybdenum or tungsten, as well as oxygen-containing organic compound is a hydrate of oxalic acid in their molar ratio equal to 1:(0,33÷1,50).