CZ310090B6 - A method of preparation of sub-micron and/or micron fibres consisting of crystalline titanium dioxide - Google Patents

Abstract

The method of preparation of sub-micron and/or micron fibres consisting of crystalline TiO2 is described, when the spinning of the solution for the spinning and formation of precursory fibres, which contains 5 to 15 wt. % of bis(oxalato)oxotitanate, 30 to 40 wt. % of hydrogen peroxide, 30 to 40 wt. % of water, 10 to 25 wt. % of polyvinylpyrrolidone with molar mass of 360,000 to 1,300,000 g/mol or 8 to 15 wt. % of polyethylene glycol with molar mass of 200,000 to 700,000 g/mol or 10 to 20 wt. % of the mixture of polyvinylpyrrolidone and polyethylene glycol in the mass ratio of 2:1 to 5:1 is used in the preparation of precursory fibres with 400 to 5800 nm in diameter. These precursory fibres are calcined at 450 to 650 °C for 45 to 75 minutes, whereas carrier polymer(s) and organic constituents are burned out from their structure and ammonium bis(oxalato)peroxotitanate is decomposed and the formed titanium is oxidised to crystalline TiO2, which preserves the fibrous structure of the precursory fibres. That way the sub-micron and/or micron fibres consisting of crystalline TiO2 with 250 to 1850 nm in diameter are formed.

Description

Method of preparation of submicron and/or micron fibers formed by crystalline titanic oxide

Field of technology

The invention relates to a method of preparing submicron and/or micron fibers formed by crystalline titanium oxide (TiO?).

Current state of the art

Due to its photocatalytic [1 and 3], sensory [4] and optical [5] properties and high biocompatibility [6], titanium dioxide (TiO?) is of great interest in various applications. Currently, under laboratory conditions, TiO? it is commonly prepared in several different submicron forms, such as nanoparticles, nanotubes and nanofibers.

Usual method of preparation of TiO nanofibers? or in electrostatic fiberization [7 to 12] or centrifugal fiberization [13] of a suitable precursor solution and further processing of precursor fibers prepared in this way with the help of high-temperature firing to the desired crystalline TiO? in the form of nanofibers. The precursor solution contains an organometallic titanium precursor, such as titanium butoxide, or titanium isopropoxide and a suitable carrier polymer, usually polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), etc. Organic solvents are used as solvents, such as ethanol, methanol, dimethylacetamide, etc. Various additives also appear in some publications, e.g. inorganic acids and salts. This method of preparing TiO nanofibers? is described in great detail in the review article [1?].

Another way to prepare TiO nanofibers? represents the hydrothermal method [14], or templating.

Overall, it can be concluded that none of these procedures is applicable on an industrial scale due to the technologies used, because it is difficult to carry them out on an industrial scale while maintaining fiber quality and production economy; at the same time, none of them is ecological due to the raw materials used.

The aim of the invention is to propose methods of preparing submicron and/or micron fibers formed by crystalline TiO?, which would eliminate the disadvantages of the state of the art.

List of non-patent literature

[1] A.L. Linsebigler, G. Lu, J.T. Yates, Photocatalysis on TiO? surfaces: principles, mechanisms, and selected results, Chem. Rev. 95 (1995) 735-758.

[?] M. Anpo, S. Dohshi, M. Kitano, Y. Hu, M. Takeuchi, M. Matsuoka, The preparation and characterization of highly efficient titanium oxide-based photofunctional materials, Annu. Rev. Mater. Res. 35 (?005) 1-?7.

[3] J.M. Macak, M. Zlamal, J. Krysa, P. Schmuki, Self-organized TiO? nanotube layers as highly efficient photocatalysts, Small 3 (?007) 300-304.

[4] P. M. Perillo, D. F. Rodriguez, The gas sensing properties at room temperature of TiO? nanotubes by anodization, Sensor. Actuator. B-Chem, 171(?01?) 639-643.

- 1 CZ 310090 B6

[5] E.Manea et al., Antireflective Coatings with Nanostructured TiCL Thin Films for Silicon Solar Cells, Journal of Nano Research 21 (2012) 89-94.

[6] Z. Fei Yin, L. Wu, H. Gui Yang, Y. Hua Su, Recent progress in biomedical applications of titanium dioxide, Phys. Chem. Chem. Phys. 15 (2013) 4844.

[7] X. Zhang, S. Xu, G. Han, Fabrication and photocatalytic activity of TiCF nanofiber membrane, Materials Letters 63 (2009) 1761-1763.

[8] J. Li et al., Electrospinning Synthesis and Photocatalytic Activity of Mesoporous TiO? Nanofibers, ScientificWorid Journal, Volume 2012, Article ID 154939.

[9] M. Zukalova et al., Facile Conversion of Electrospun TiCF into Titanium Nitride/Oxynitride Fibers, Chem. Mater. 22 (2010) 4045-4055.

[10] H. Hou et al., Efficient Photocatalytic Activities of T1O2 Hollow Fibers with Mixed Phases and Mesoporous Walls, Scientific Reports 5 (2015) 15228.

[11] A. S. Yasin et al., Influence of TixZr(l_x)O2 nanofibers composition on the photocatalytic activity towards organic pollutants degradation and water splitting, Ceramics International 41(2015)11876-11885.

[12] A.A. Altaf et al., Titania nano-fibers: A review on synthesis and utilities Inorganica Chimica Acta 501 (2020) 119268.

[13] H. Vasquez, H. Gutierrez, K. Lozano, G. Leal, Titanium Dioxide Nanofibers through Forcespinning, Journal of Engineered Fibers and Fabrics 10 (2015) 129-136.

[14] Y. Suzuki, S. Pavasupree, S. Yoshikawa, R. Kawahata, Natural rutile-derived titanate nanofibers prepared by direct hydrothermal processing, J. Mater. Res., 20 (2005) 1063-1070.

The essence of the invention

The aim of the invention is achieved by the preparation of submicron and/or micron fibers 0 with a diameter of 250 to 1850 nm made of crystalline titanic oxide (T1O2), in which ammonium bisoxalato-oxotitanate (C4HnNOnTi) is used as a T1O2 precursor, and polyvinylpyrrolidone (PVP) with molar with a weight of 360,000 to 1,300,000 g/mol, polyethylene glycol (PEG) with a molar weight of 200,000 to 700,000 g/mol or a mixture of PVP and PEG in a 2:1 to 5:1 porner. Therefore, it is true that with the growing molar mass of the carrier polymer/polymers, the diameter of the prepared fibers decreases.

In the method of preparing submicron and/or micron fibers formed by crystalline T1O2 according to the invention, a solution for fiberization and the formation of precursor fibers is either prepared directly by mixing all the components, or a stock solution of titanium without carrier polymer/polymers is prepared separately and then mixed with another components of the solution for fiberization and the formation of precursor fibers. Water, possibly in combination with acetic or citric acid, and hydrogen peroxide are used as a solvent for the preparation of the solution for fiberization and possibly also the titanium stock solution. Below, examples 1 to 4 describe the procedure with the direct preparation of a solution for fiberization and the formation of precursor fibers, and examples 5 to 7 describe the procedure using a titanium stock solution.

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Procedure without using titanium stock solution

The solution for fiberization and the formation of precursor fibers is prepared by dissolving bisoxylâtooxotitanate (5 to 15% by weight of the resulting solution) in technical peroxide (with an advantage of 30%) (30 to 40% by weight of the resulting solution) and water (30 to 40% by weight of the resulting solution solution), preferably with the addition of citric or acetic acid (from 12% by weight of the resulting solution). The mixture created in this way is stirred with a magnetic stirrer at elevated temperatures (40 ± 5 °C) until the bisoxalate-oxotitanate is completely dissolved and a clear solution of the peroxocomplex is formed. Then let it cool freely to room temperature. After cooling, PVP with a molar mass of 360,000 to 1,300,000 g/mol is added to it in an amount of 10 to 25% by weight. of the resulting solution or PEG with a molar mass of 200,000 to 700,000 g/mol in an amount of 8 to 15% by weight. of the resulting solution or a mixture of PVP and PEG in a ratio of 2:1 to 5:1 in the amount of 10 to 20% by weight. of the resulting solution, and the rest up to 100 wt.% top up with water. The order of adding PVP and PEG does not matter. The mixture created in this way is then mixed until a homogeneous solution is formed.

In order to reduce the surface tension and facilitate the initiation of fiberization, it is possible to add ethanol to this mixture in addition to water, in an amount of up to 20% by weight.

Alternatively, it is possible to add acetic or citric acid and/or water to the mixture of ammonium bisoxalâto-oxotitanâtu in technical hydrogen peroxide before forming the solution. The order of adding the individual components does not matter.

Procedure using titanium stock solution

In this case, the preparation of the solution for fiberization and the formation of precursor fibers takes place in two steps.

Step 1: preparation of titanium stock solution

A titanium stock solution with a titanium concentration of 0.3 to 0.65 M is prepared by dissolving the appropriate amount of ammonium bisoxalâto-oxotitanât in technical hydrogen peroxide. The mixture created in this way is intensively stirred at elevated temperatures (40 ± 5 °C) until the bisoxal-tooxotitanate is completely dissolved and a clear solution of the peroxocomplex is formed. Ammonium bisoxalato oxotitanât is oxidized by hydrogen peroxide to bisoxalâto peroxotitanât, resulting in the formation of an orange-red clear solution. After cooling the solution to room temperature (with the benefit of free air), acetic acid (CHaCOOH) or citric acid (C6H8O7) is added to it in an amount of up to 12% by weight, which stabilizes the titanium stock solution and at the same time has a positive effect on the arrangement of the crystals and thus on the size of the specific surface of the created fibers, and possibly also water in the amount to the required volume, whereby the total water content in the stock solution is up to 40% by weight. When creating a titanium stock solution for immediate consumption, the addition of acetic acid is not necessary. Alternatively, it is possible to add acetic or citric acid and/or water to the mixture of ammonium bisoxalâto-oxotitanâtu in technical hydrogen peroxide, before forming the solution. The order of adding the individual components does not matter.

The advantage of the titanium stock solution prepared in this way is that, thanks to the absence of ethanol, it is stable and usable for a long time (up to 2 months).

Step 2: preparation of the solution for fiberization and formation of precursor fibers

PVP with a molar mass of 360,000 to 1,300,000 g/mol in the amount of 10 to 25% by weight is added to the titanium stock solution prepared in this way. of the resulting solution or PEG with a molar mass of 200,000 to 700,000 g/mol in an amount of 8 to 15% by weight. of the resulting solution or a mixture of PVP and PEG in a ratio of 2:1 to 5:1 in the amount of 10 to 20% by weight. of the resulting solution, and the rest up to 100 wt.% top up with water. The order of adding PVP and PEG does not matter. Like this

- 3 CZ 310090 B6 the resulting mixture is then mixed until a homogeneous solution is formed. The concentration of the polymer/polymers in this solution is 5 to 25% by weight. If necessary, this solution is supplemented with water to the required volume. The share of water is up to 40% by weight.

In order to reduce the surface tension and facilitate the initiation of fiberization, it is possible to add ethanol to this mixture in addition to water, in an amount of up to 20% by weight.

The solution for fiberization and formation of precursor fibers prepared by one of the methods described above is then fiberized using a suitable fiberization technology. Centrifugal fiberization, which does not require high electrical voltage, and in which large and easy-to-manipulate clumps of precursor fibers without electrical charge are deposited on the collectors, thus eliminating the need to laboriously peel the fiber from the base material (e.g. non-woven fabric) appears to be the most suitable. , such as e.g. when using electrostatic fiberization. Another advantage of centrifugal fiberization is that it has a greater yield of fibers in time than other methods, such as electrostatic fiberization, hydrothermal processes, templating, drawing, etc. and makes it possible to prepare industrial quantities of material in a short time. In addition to this technology, however, any other known technology for the preparation of submicron or micron fibers can be used for the production of submicron or micron fibers, especially electrostatic fiberization.

When the conditions of centrifugal fiberization are properly set, air with a temperature of 25 to 45 °C and a relative humidity of 15 to 40% flows into the fiberization chamber, and the fiberization head rotates at a speed of 1000 to 10,000/min, with an output of 2,000 to 7,000/min.

The diameters of precursor fibers prepared by centrifugal fiberization reach approx. 400 to 5800 nm.

The precursor fibers prepared in this way are then calcined, whereby their organic components are removed by heat and the ammonium bisoxalâto-oxotitanât is transformed into crystalline TiO2, which preserves the fiber structure of the precursor fibers and creates submicron and/or micron fibers with a diameter between 250 and 1850 nm. Calcination can generally take place in the temperature range of 450 to 650 °C, when both the decomposition of the carrier polymer(s) and the conversion of bisoxalâto-oxotitanât occur. The precursor fibers remain at the calcination temperature for 45 to 75 minutes. A suitable temperature increase during calcination is 0.5 to 5 °C/min.

Submicron and/or micron fibers prepared in this way have high mechanical integrity and excellent textural properties with a unique porous 3D structure. Due to their structure, they have a large surface area (up to 100 m ² /g), which is key to their activity and reactivity in binding applications.

Clarification of the drawing

In the provided drawings, fig. 1 SEM image of submicron fibers formed by crystalline TiO2 according to the invention at a magnification of 2000 times and in fig. 2 SEM images of the same submicron fibers at a magnification of 15,000 times. In fig. 3 is an SEM image of micron fibers formed by crystalline TiO2 according to the invention at a magnification of 2000 times and in fig. 4 SEM images of the same micron fibers at a magnification of 80,000 times. In fig. 5 is an SEM image of micron fibers formed by crystalline TiO2 according to the invention at a magnification of 2000 times and in fig. 6 SEM image of these micron fibers at a magnification of 100,000 times. In fig. 7 is an X-ray diffractogram of submicron fibers made of crystalline TiO2, which proves that the fibers have a crystalline structure of anatase and rutile.

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Examples of the implementation of the invention

For clarity, 9 specific examples of the preparation of submicron and/or micron fibers made of crystalline TiO2 according to the invention are given below.

Examples 1 to 5 describe a variant with the preparation of a solution for fiberization and the formation of precursor fibers without a titanium stock solution. Examples 6 to 9 describe a variant with the preparation of a titanium stock solution.

In all examples, the fibers were characterized by electron microscopy before and after calcination. Image analysis for the evaluation of the average was performed with the help of the software on a minimum of 4 images from an electron microscope for each sample with a minimum number of measurements n >60.

Example 1

0.6 g (approx. 5% by weight) of ammonium bisoxalâto-oxotitanât (C4HiiNOiiTi), 4 g (approx. 33.1% by weight) of 30% technical peroxide, 3.4 g of water (approx. 28.1% by weight) and 0.6 g (approx. 5% by weight) of citric acid (C6HsO?). The mixture created in this way was heated to a temperature of 35 °C and intensively stirred with a magnetic stirrer until the formation of an orange-red clear solution of the peroxo complex (approx. 30 minutes). Then, with constant stirring, this solution was allowed to cool freely to room temperature, when 0.5 g (approx. 4.1% by weight) of 96% ethanol and 3 g (approx. 24.8% by weight) of PVP (K90 ).

The solution for fiberization prepared in this way was fiberized on a Cyclone G1 centrifugal fiberization laboratory equipment (manufactured by Pardam). The spinning heads were set to 2000/min, the relative humidity in the device chamber was 15%, and the temperature was 40°C. 1.6 g of precursor fibers with a diameter of 1023 ±169 nm were prepared by spinning.

0.923 g of these precursor fibers were then placed in a ceramic crucible. In it, this fiber was heated to a temperature of 450 °C at a speed of 3 °C/min and remained there for 75 minutes. In doing so, all organic components were removed from the fibers and ammonium bisoxalâto-oxotitanât was transformed into TiO2. Free cooling to room temperature followed. The result was 0.048 g of fibers made of crystalline TiO2 with a diameter of 629 ±293 nm - see fig. 1, which shows an SEM image of these fibers at a magnification of 2000 times, and fig. 2, which shows a SEM image of these fibers at a magnification of 15,000 times. In fig. 7 is an X-ray diffractogram of submicron fibers made of crystalline TiO2, which proves that the fibers have a crystalline structure of anatase and rutile.

Example 2

0.6 g (approx. 5% by weight) of ammonium bisoxalâto-oxotitanât (C4H11NO11Ti), 4 g (approx. 32.8% by weight) of 30% technical peroxide and 4.6 g (approx. 37 .7% by weight) of water. The mixture created in this way was heated to a temperature of 40 °C and intensively stirred with a magnetic stirrer until the formation of an orange-red clear solution of the peroxocomplex (approx. 30 minutes). Then, with constant stirring, this solution was allowed to cool freely to room temperature, when 1.2 g (approx. 9.8% by weight) of 96% ethanol and 1.8 g (approx. 14.8% by weight) of PEG were added to it. .

The solution for fiberization prepared in this way was fiberized on a Cyclone G1 centrifugal fiberization laboratory equipment (manufactured by Pardam). The spinning heads were set to 6000/min, the relative humidity in the device chamber was 15%, and the temperature was 40°C. 0.8 g of precursor fibers with a diameter of 600 ±144 nm were prepared by spinning.

0.486 g of these precursor fibers were then placed in a ceramic crucible. In it, this fiber was heated to a temperature of 650 °C at a speed of 5 °C/min and remained there for 45 minutes. At the same time, from the fibers

- 5 CZ 310090 B6 removed all organic components and ammonium bisoxalâto-oxotitanât was transformed into TiO2. Free cooling to room temperature followed. The result was 0.032 g of TiO2 fibers with a diameter of 388 ±176 nm.

Example 3

0.6 g (approx. 4.8% by weight) of ammonium bisoxalâtooxotitanât (C4HiiNOiiTi), 4 g (approx. 32.0% by weight) of 30% technical peroxide and 5.7 g (approx. 45 .6% by weight) of water. The mixture created in this way was heated to a temperature of 40 °C and intensively stirred with a magnetic stirrer until the formation of an orange-red clear solution of the peroxocomplex (approx. 30 minutes). Then, with constant stirring, this solution was allowed to cool freely to room temperature, when 1.2 g (approx. 9.6% by weight) of 96% ethanol and 1.0 g (approx. 8.0% by weight) of PEG were added to it. .

The solution for fiberization prepared in this way was fiberized on a Cyclone G1 centrifugal fiberization laboratory equipment (manufactured by Pardam). The spinning heads were set to 6000/min, the relative humidity in the device chamber was 15%, and the temperature was 40°C. By spinning, 0.6 g of precursor fibers with a diameter of 488 ±132 nm were prepared.

0.423 g of these precursor fibers were then placed in a ceramic crucible. In it, this fiber was heated to a temperature of 650 °C at a speed of 5 °C/min and remained there for 45 minutes. In doing so, all organic components were removed from the fibers and ammonium bisoxalâto-oxotitanât was transformed into TiO2. Free cooling to room temperature followed. The result was 0.025 g of TiO2 fibers with a diameter of 365 ±155 nm.

Example 4

1.2 g (approx. 9.4% by weight) of ammonium bisoxalâtooxotitanât (C4HiiNOiiTi), 4 g (approx. 31.3% by weight) of 30% technical peroxide and 4 g (approx. 31.3 % wt.) of water. The mixture created in this way was heated to a temperature of 45 °C and intensively stirred with a magnetic stirrer until the formation of an orange-red clear solution of the peroxocomplex (approx. 30 minutes). Then, with constant stirring, this solution was allowed to cool freely to room temperature, when 1.2 g (approx. 9.4% by weight) of 96% ethanol and 2.4 g (approx. 18.8% by weight) of PVP were added to it. (K90).

The solution for fiberization prepared in this way was fiberized on a Cyclone G1 centrifugal fiberization laboratory equipment (manufactured by Pardam). The spinning heads were set to 2500/min, the relative humidity in the device chamber was 15%, and the temperature was 40°C. 1.5 g of precursor fibers with a diameter of 1785 ±502 nm were prepared by spinning.

1.031 g of these precursor fibers were subsequently placed in a ceramic crucible. In it, this fiber was heated to a temperature of 450 °C at a speed of 0.5 °C/min and remained there for 60 minutes. In doing so, all organic components were removed from the fibers and ammonium bisoxalâto-oxotitanât was transformed into TiO2. Free cooling to room temperature followed. The result was 0.087 g of TiO2 fibers with a diameter of 845 ±393 nm.

Example 5

4.8 g (approx. 11.1% by weight) of ammonium bisoxalâtooxotitanât (C4H11NO11Ti), 16 g (approx. 37% by weight) of 30% technical peroxide, 8 g (approx. 18.5% by weight) were placed in a beaker with a volume of 50 ml .) of water and 3 g (approx. 6.9% by weight) of 100% acetic acid. The mixture created in this way was heated to a temperature of 40 °C and intensively stirred with a magnetic stirrer until an orange-red clear solution of the peroxocomplex was formed (approx. 30 minutes). Then, with constant stirring, this solution was allowed to cool freely to room temperature, when 7 g (approx. 16.2% by weight) of 96% ethanol and 4.5 g (approx. 10.4% by weight) of PVP (K90 ).

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The fiberization solution prepared in this way was fiberized on a Cyclone G1 centrifugal fiberization laboratory equipment (manufactured by Pardam). The spins of the fiberizing head were set to 3000/min, the relative humidity in the device chamber was 15%, and the temperature was 40 °C. 3.8 g of precursor fibers with a diameter of 1271 ±387 nm were prepared by spinning.

0.848 g of these precursor fibers were subsequently placed in a ceramic crucible. In it, this fiber was heated to a temperature of 450 °C at a speed of 3 °C/min and remained there for 60 minutes. In doing so, all organic components were removed from the fibers and ammonium bisoxalâto-oxotitanât was transformed into TiÜ2. Free cooling to room temperature followed. The result was 0.062 g of TiÜ2 fibers with a diameter of 691 ±267 nm.

Example 6

The solution for fiberization and preparation of precursor fibers was prepared in two steps. In the first step, a titanium stock solution with a titanium concentration of 0.44M stabilized with acetic acid was prepared. The stock solution prepared in this way was stable for several weeks. In the second step, part of the stock solution was taken and mixed with the carrier polymer - in this case PVP and PEG.

Step 1

Preparation of titanium stock solution with a concentration of 0.44M.

6 g (12% by weight) of ammonium bisoxalâto-oxotitanât (C4HiiNOiiTi) and 20 g (40% by weight) of 30% technical peroxide were placed in a beaker with a volume of 50 ml. The mixture created in this way was heated to a temperature of 40 °C and intensively stirred with a magnetic stirrer until the formation of an intensely red clear solution of the peroxocomplex (approx. 30 minutes). Then this solution was allowed to cool freely to room temperature. The solution thus prepared was transferred to a volumetric flask with a volume of 50 ml, where 2.5 g (5% by weight) of 100% acetic acid (CHaCOOH) was added to it, and then 21.5 g (43% by weight) of water was added. up to the total weight of the solution 50 g. This prepared a titanium stock solution with a titanium molar concentration of 0.44 mmol/g.

Step 2

15 g (approx. 71.8% by weight) of the titanium stock solution prepared in step 1 was poured into a beaker with a volume of 100 ml, and 1.2 g (approx. 5.7% by weight) of 96% ethanol, 1.25 g (approx. 6% by weight) of PEG and 3.45 g (approx. 16.5% by weight) of PVP (K90). The order of adding PEG and PVP does not matter. This mixture was subsequently stirred for 3 hours and the resulting solution was further processed on the same day.

The fiberization solution prepared in this way was fiberized on a Cyclone G1 centrifugal fiberization laboratory equipment (manufactured by Pardam). The spinning heads were set to 5000/min, the relative humidity in the device chamber was 15%, and the temperature was 40°C. 2.6 g of precursor fibers with a diameter of 3253 ±982 nm were prepared by spinning.

1.153 g of these precursor fibers were subsequently placed in a ceramic crucible. In it, this fiber was heated to a temperature of 450 °C at a speed of 3 °C/min and remained there for 60 minutes. In doing so, all organic components were removed from the fibers and ammonium bisoxalâto-oxotitanât was transformed into TiO2. Free cooling to room temperature followed. The result was 0.069 g of TiO2 fibers with a diameter of 1161 ±289 nm - see fig. 3, which shows an SEM image of these fibers at a magnification of 2000 times, and fig. 4, which shows an SEM image of these fibers at a magnification of 80,000 times.

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Example 7

The solution for fiberization and preparation of precursor fibers was prepared in two steps. In the first step, a titanium stock solution with a titanium concentration of 0.6 M stabilized with acetic acid was prepared. The stock solution prepared in this way was stable for several weeks. In the second step, part of the stock solution was taken and mixed with a carrier polymer - in this case PVP and PEG.

Step 1

Preparation of titanium stock solution with a concentration of 0.6M.

8.2 g (approx. 16.4% by weight) of ammonium bisoxalâtooxotitanât (C4HiiNOiiTi) and 27.3 g (approx. 54.6% by weight) of 30% technical peroxide were placed in a beaker with a volume of 50 ml. The mixture created in this way was heated to a temperature of 40 °C and intensively stirred with a magnetic stirrer until the formation of an intensely red clear solution of the peroxocomplex (approx. 30 minutes). Then this solution was allowed to cool freely to room temperature. The solution thus prepared was transferred to a volumetric flask with a volume of 50 ml, where 3 g (6% by weight) of 100% acetic acid (CHaCOOH) was added to it, and then 11.5 g (23% by weight) of water was added to the total weight of the solution 50 g. This prepared a titanium stock solution with a titanium molar concentration of 0.6 mmol/g.

Step 2

15 g (approx. 60.7% by weight) of the titanium stock solution prepared in step 1 was poured into a beaker with a volume of 100 ml, and 5 g (approx. 20.2% by weight) of 96% ethanol, 3.25 g ( approx. 13.2% by weight) of PEG and 3.45 g (approx. 14% by weight) of PVP (K90). The order of adding PEG and PVP does not matter. This mixture was subsequently stirred for 3 hours and the resulting solution was further processed the same day.

The solution for fiberization prepared in this way was fiberized on a Cyclone G1 centrifugal fiberization laboratory equipment (manufactured by Pardam). The spinning heads were set to 6000/min, the relative humidity in the device chamber was 15%, and the temperature was 40°C. 2.9 g of precursor fibers with a diameter of 3642 ±1297 nm were prepared by spinning.

2.165 g of these precursor fibers were subsequently placed in a ceramic crucible. In it, this fiber was heated to a temperature of 450 °C at a speed of 3 °C/min and remained there for 60 minutes. In doing so, all organic components were removed from the fibers and ammonium bisoxalâto-oxotitanât was transformed into TiO2. Free cooling to room temperature followed. The result was 0.097 g of TiO2 fibers with a diameter of 1318 ±299 nm - see fig. 5, which shows an SEM image of these fibers at a magnification of 2000 times, and fig. 6, which shows an SEM image of these fibers at a magnification of 100,000 times.

Example 8

The solution for fiberization and preparation of precursor fibers was prepared in two steps. In the first step, a titanium stock solution with a titanium concentration of 0.65 M stabilized with acetic acid was prepared. The stock solution prepared in this way was stable for several weeks. In the second step, part of the stock solution was taken and mixed with a carrier polymer - in this case PVP and PEG.

Step 1

Preparation of titanium stock solution with a concentration of 0.65M.

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9 g (18% by weight) of ammonium bisoxalâto-oxotitanât (C4HiiNOiiTi) and 27.3 g (54.6% by weight) of 30% technical peroxide were placed in a beaker with a volume of 50 ml. The mixture created in this way was heated to a temperature of 40 °C and intensively stirred with a magnetic stirrer until the formation of an intensely red clear solution of the peroxocomplex (approx. 30 minutes). Then this solution was allowed to cool down to room temperature. The solution thus prepared was transferred to a volumetric flask with a volume of 50 ml, where 6 g (12% by weight) of 100% acetic acid (CHaCOOH) was added to it, and then 7.7 g (15.4% by weight) of water was added. up to the total weight of the solution 50 g. This prepared a titanium stock solution with a titanium molar concentration of 0.65 mmol/g.

Step 2

15 g (approx. 57.3% by weight) of the titanium solution prepared in step 1 was poured into a beaker with a volume of 100 ml, and 6.5 g (approx. 24.8% by weight) of 96% ethanol, 1.25 g (approx. 4.8% by weight) of PEG and 3.45 g (approx. 13.2% by weight) of PVP (K90). The order of adding PEG and PVP does not matter. This mixture was subsequently stirred for 3 hours and the resulting solution was further processed the same day.

The solution for fiberization prepared in this way was fiberized on a Cyclone G1 centrifugal fiberization laboratory device (manufactured by Pardam). The spinning heads were set to 7000/min, the relative humidity in the device chamber was 15%, and the temperature was 40°C. 2.4 g of precursor fibers with a diameter of 4264 ±1466 nm were prepared by spinning.

0.998 g of these precursor fibers were subsequently placed in a ceramic crucible. In it, this fiber was heated to a temperature of 450 °C at a speed of 3 °C/min and remained there for 60 minutes. In doing so, all organic components were removed from the fibers and ammonium bisoxalâto-oxotitanât was transformed into TiO2. Free cooling to room temperature followed. The result was 0.062 g of TiO2 fibers with a diameter of 1345 ±415 nm.

Example 9

The solution for fiberization and preparation of precursor fibers was prepared in two steps. In the first step, a titanium stock solution with a titanium concentration of 0.65 M stabilized with acetic acid was prepared. The stock solution prepared in this way was stable for several weeks. In the second step, part of the stock solution was taken and mixed with a carrier polymer - in this case PVP and PEG.

Step 1

Preparation of titanium stock solution with a concentration of 0.65M.

9 g (18% by weight) of ammonium bisoxalâto-oxotitanât (C4H11NO11Ti) and 27.3 g (54.6% by weight) of 30% technical peroxide were placed in a beaker with a volume of 50 ml. The mixture created in this way was heated to a temperature of 40 °C and intensively stirred with a magnetic stirrer until the formation of an intensely red clear solution of the peroxocomplex (approx. 30 minutes). Then this solution was allowed to cool down to room temperature. The solution thus prepared was transferred to a volumetric flask with a volume of 50 ml, where 6 g (12% by weight) of 100% acetic acid (CHaCOOH) was added to it, and then 7.7 g (15.4% by weight) of water was added. up to the total weight of the solution 50 g. This prepared a titanium stock solution with a titanium molar concentration of 0.65 mmol/g.

Step 2

15 g (approx. 62.8% by weight) of the titanium solution prepared in step 1 was poured into a 100 ml beaker and 6.5 g (approx. 27.2% by weight) of 96% ethanol, 0.7 g (approx. 2.9% by weight) of PEG and 1.7 g (approx. 7.1% by weight) of PVP (K90). The order of adding PEG and PVP does not matter. This mixture was subsequently stirred for 3 hours and the resulting solution was further processed the same day.

- 9 CZ 310090 B6

The solution for fiberization prepared in this way was fiberized on a Cyclone G1 centrifugal fiberization laboratory equipment (manufactured by Pardam). The spinning heads were set to 4000/min, the relative humidity in the device chamber was 15%, and the temperature was 40°C. 1.3 g of precursor fibers with a diameter of 812 ±236 nm were prepared by spinning.

0.611 g of these precursor fibers were subsequently placed in a ceramic crucible. In it, this fiber was heated to a temperature of 450 °C at a speed of 3 °C/min and remained there for 60 minutes. In doing so, all organic components were removed from the fibers and ammonium bisoxalâto-oxotitanât was transformed into TiÜ2. Free cooling to room temperature followed. The result was 0.036 g of TiÜ2 fibers with a diameter of 442 ±174 nm.

Claims (8)

1. A method of preparing submicron and/or micron fibers formed by crystalline TiO2, characterized by the fiberization of the solution for fiberization and the formation of precursor fibers, which contains 5 to 15 wt.%. bisoxalâto-oxotitanâtu, 30 to 40 wt.% of hydrogen peroxide, 30 to 40% by weight of water, 10 to 25% by weight of polyvinylpyrrolidone with a molar mass of 360,000 to 1,300,000 g/mol or 8 to 15% by weight. of polyethylene glycol with a molar mass of 200,000 to 700,000 g/mol or 10 to 20 wt.%. mixtures of polyvinylpyrrolidone and polyethylene glycol in a mass ratio of 2:1 to 5:1 prepare precursor fibers with a diameter of 400 to 5800 nm, and these precursor fibers are calcined at a temperature of 450 to 650 °C for a period of 45 to 75 minutes to form submicron and/or micron fibers with a diameter of 250 to 1850 nm formed by crystalline TiO2. 2. The method of preparing submicron and/or micron fibers according to claim 1, characterized by the fact that bisoxalate-oxotitanate in an amount corresponding to a concentration of 0.3 to 0.65 M is mixed with hydrogen peroxide, whereby the mixture created in this way is heated to a temperature of 40 ± 5 °C and mixed until the bisoxalate-oxotitanate is completely dissolved, obtaining a titanium stock solution, then polyvinylpyrrolidone with a molar mass of 360,000 to 1,300,000 g/mol is added to the thus prepared titanium stock solution in an amount of 10 to 25% by weight. of the resulting solution or polyethylene glycol with a molar mass of 200,000 to 700,000 g/mol in an amount of 8 to 15% by weight. of the resulting solution or a mixture of polyvinylpyrrolidone and polyethylene glycol in a weight ratio of 2:1 to 4:1 in a total amount of 10 to 20% by weight. of the resulting solution, and the rest up to 100 wt.% is supplemented with water, the mixture created in this way is subsequently mixed until a homogeneous solution is formed. 3. The method of preparing submicron and/or micron fibers according to claim 2, characterized by the fact that up to 20% by weight of ethanol is added to the titanium stock solution after its preparation or during its preparation 4. The method of preparing submicron and/or micron fibers according to claim 2 or 3, characterized by the fact that up to 12% by weight is added to the titanium stock solution after its preparation or during its preparation. acetic or citric acid. 5. The method of preparing submicron and/or micron fibers according to claim 1, characterized in that the solution for fiberization and the formation of precursor fibers is prepared by mixing bisoxylátooxotitanate in an amount of 5 to 15 wt.%. of the resulting solution, peroxide in the amount of 30 to 40% by weight. of the resulting solution and water in the amount of 30 to 40% by weight. of the resulting solution, the mixture created in this way is heated to a temperature of 40 ± 5 °C and mixed until the bisoxalate-oxotitanate is completely dissolved, and after its complete dissolution, polyvinylpyrrolidone with a molar mass of 360,000 to 1,300,000 g/mol is added to the solution prepared in this way in the amount of 10 to 25% wt. of the resulting solution or polyethylene glycol with a molar mass of 200,000 to 700,000 g/mol in an amount of 8 to 15% by weight. of the resulting solution or a mixture of polyvinylpyrrolidone and polyethylene glycol in a weight ratio of 2:1 to 5:1 in a total amount of 10 to 20% by weight. of the resulting solution, and the rest up to 100 wt.% top up with water. - 11 CZ 310090 B6 6. The method according to claim 5, characterized by the fact that up to 20% by weight is added to the solution for fiberization and the formation of precursor fibers after its preparation or during its preparation. ethanol. 7. The method of preparing submicron and/or micron fibers according to claim 5 or 6, characterized in that up to 12% by weight is added to the solution for fiberization and the formation of precursor fibers after its preparation or during its preparation. acetic or citric acid. 8. Method according to any one of claims 1 to 7, characterized in that the solution for fiberization and the formation of precursor fibers is fiberized by centrifugal fiberization.