Magnetic titanium dioxide material and its preparation method

Abstract

The present invention discloses a magnetic titanium dioxide material and a preparation method thereof. Among them, the method includes: (1) mixing tetrabutyl titanate with a fluoride ion-containing solution; (2) performing a hydrothermal reaction on the mixed solution, and then separating the solid from the liquid to obtain a white precipitate and waste liquid; (3) washing and drying the white precipitate to obtain a TiO2{001}-{101} crystal plane heterojunction; (4) performing heat treatment on the TiO2{001}-{101} crystal plane heterojunction in an inert atmosphere to obtain a magnetic titanium dioxide material. Thus, a pure magnetic titanium dioxide material can be prepared by using this method, and the magnetism of the magnetic titanium dioxide material can be adjusted. At the same time, this method is simple to operate, energy-saving and emission-reducing, low in cost, and suitable for mass production.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic materials, and particularly relates to a magnetic titanium dioxide material and a preparation method thereof. Background Art

[0002] Magnetic materials are a very important type of basic functional materials in the material field, and their application fields are very broad. Magnetic materials play an irreplaceable role in industries such as information, electronics, medicine, automobiles, power tools, and household appliances. Moreover, with the rapid development of society, the environmental pollution problems caused by the extensive use of traditional energy sources such as coal, oil, and natural gas seriously threaten the safety of the ecological system; and the energy shortage problems caused by the non-renewability of fossil energy further restrict the rapid development of human civilization. Carbon peak and carbon neutrality have been incorporated into the overall layout of ecological civilization construction. The work of carbon peak and carbon neutrality requires controlling the consumption of fossil energy and accelerating the development of the green energy industry. As a clean energy, magnetic materials will be more and more widely used in emerging fields such as new energy, energy conservation and environmental protection, electric vehicles, smart cities, and smart earth; magnetic materials have even begun to be applied in military and defense fields such as unmanned aerial vehicles, robots, aerospace, and satellite remote sensing. As one of the key development fields of the country, the development of magnetic materials is highly supported by national policies.

[0003] At present, magnetic materials include two major categories: metal magnetic materials and non-metal magnetic materials. Metal magnetic materials are relatively expensive and are mostly used in the fields of military and high-end electronic products. The high cost seriously affects the development of the application fields of metal magnetic materials and the promotion of new markets. Compared with metal magnetic materials, non-metal magnetic materials are widely used in various fields because of their low price and stable performance, and can be used in relatively harsh environments. Ferrite permanent magnet materials are the most important type of non-metal permanent magnet materials at present. Their preparation process is simple and mature, the price is low, and the price per unit magnetic energy product is low. They have the advantages of corrosion resistance and being able to be applied to harsh working environments, so they are widely used in fields such as electronics, electrical, machinery, transportation, medical treatment, and daily necessities. However, ferrite permanent magnet materials also have many disadvantages, mainly including: 1) The remanence density is not high, and the maximum magnetic energy product is not high, so it is necessary to increase the cross-sectional area of the magnetic flux provided, resulting in a relatively large volume of the motor; 2) The environmental temperature has a great influence on the magnetic properties, so it is necessary to check and calculate the minimum temperature and maximum demagnetization working point during use to prevent irreversible demagnetization at low temperatures; 3) They are hard and brittle and cannot be processed electrically. Therefore, it is necessary to develop new magnetic materials.

[0004] The patent document with the publication number CN107149918A discloses a method for preparing magnetic titanium dioxide hollow microspheres. In this method, ferric chloride hexahydrate is used as the iron source, and after being treated with an epoxy silane coupling agent, a cyclic iron source solution is obtained. Then, tetrabutyl titanate is used as the precursor, which is treated in an ethanol solution of trimethylolpropane and then mixed with the cyclic iron source solution. Using calcium sulfate as a catalyst, through the reaction of hydroxyl groups and epoxy groups, an iron-doped sol is obtained. Then, acrylonitrile is used as the monomer, and through copolymerization with oleic acid, oleic acid-modified polyacrylonitrile is obtained. This is added to the iron-doped sol, and ammonia water is added to promote the hydrolysis of tetrabutyl titanate and generate iron hydroxide, which is deposited on the surface of the polymer. Then, trimethylolpropane is added, and under the catalysis of p-toluenesulfonic acid, through the esterification reaction of trimethylolpropane and oleic acid, magnetically doped titanium dioxide is tightly coated on the surface of the polymer. At the same time, under hydrothermal action, iron oxide is obtained. Then, the polymer is dispersed in dimethylformamide to dissolve the polymer, and hollow magnetic titanium dioxide microspheres are obtained.

[0005] The patent document with the publication number CN104353075A discloses a water-soluble magnetic titanium dioxide, its preparation method and application. This water-soluble magnetic titanium dioxide is formed by doping magnetite in titanium dioxide molecules and chemically connecting hydrophilic groups.

[0006] However, the titanium dioxide prepared by the above method is either a mixture or doped with other ions, and pure magnetic titanium dioxide cannot be obtained. Therefore, the existing magnetic titanium dioxide preparation technology needs to be improved. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this reason, an object of the present invention is to provide a magnetic titanium dioxide material and its preparation method. By using this method, pure magnetic titanium dioxide material can be prepared, and the magnetism of this magnetic titanium dioxide material is adjustable. At the same time, this method is simple to operate, energy-saving and emission-reducing, low in cost, and suitable for mass production.

[0008] In one aspect of the present invention, a method for preparing a magnetic titanium dioxide material is provided. According to an embodiment of the present invention, the method includes:

[0009] (1) Mix tetrabutyl titanate with a fluoride ion-containing solution to obtain a mixed solution;

[0010] (2) Perform a hydrothermal reaction on the mixed solution, then perform solid-liquid separation to obtain a white precipitate and waste liquid;

[0011] (3) Wash and dry the white precipitate to obtain a TiO2{001}-{101} crystal plane heterojunction;

[0012] (4) Heat-treat the TiO₂ {001}-{101} facet heterojunction in an inert atmosphere to obtain a magnetic titanium dioxide material.

[0013] According to the method for preparing a magnetic titanium dioxide material of an embodiment of the present invention, by mixing tetrabutyl titanate with a fluoride ion-containing solution and subjecting the resulting mixed solution to a hydrothermal reaction, F - adsorption can effectively reduce the surface energy of the {001} facet, making it slightly lower than the surface energy of the {101} facet, generating a TiO₂ {001}-{101} facet heterojunction with different ratios of {001} and {101} facets that precipitates from the solution in the form of a white precipitate. Then, solid-liquid separation is performed on the reaction solution to obtain a white precipitate containing the TiO₂ {001}-{101} facet heterojunction; the white precipitate is washed and dried to obtain the TiO₂ {001}-{101} facet heterojunction; finally, in an inert atmosphere, the TiO₂ {001}-{101} facet heterojunction is heat-treated, oxygen vacancies are introduced into the TiO₂ {001}-{101} facet heterojunction, and the magnetism of the material is induced by the synergistic regulation of the facet and oxygen vacancy defects, thereby obtaining a magnetic titanium dioxide material. Thus, by using the method of the present application, a pure magnetic titanium dioxide material can be prepared, that is, without doping other magnetic elements or being compounded with other magnetic materials. The prepared magnetic titanium dioxide material has good stability, and the magnitude of the magnetism can be adjusted by regulating the mixing ratio of tetrabutyl titanate and the fluoride ion-containing solution and then regulating the ratio of the {001} facet. At the same time, the method is simple to operate, energy-saving and emission-reducing, and has low cost, suitable for mass production.

[0014] In addition, the method for preparing a magnetic titanium dioxide material according to the above embodiment of the present invention may further have the following additional technical features:

[0015] According to some embodiments of the present invention, in step (1), the fluoride ion-containing solution is one of hydrofluoric acid and sodium fluoride.

[0016] According to some embodiments of the present invention, in step (1), the fluoride ion concentration in the fluoride ion-containing solution is 15-25 mol / L.

[0017] According to some embodiments of the present invention, in step (1), the volume ratio of tetrabutyl titanate to the fluoride ion-containing solution is 25:(0-15), excluding the endpoint 0.

[0018] According to some embodiments of the present invention, in step (2), the temperature of the hydrothermal reaction is 160-200 °C, and the time is 20-36 hours.

[0019] According to some embodiments of the present invention, in step (3), the cleaning is performed successively with anhydrous ethanol and water. Thereby, impurities can be avoided from being introduced during the subsequent heat treatment process.

[0020] According to some embodiments of the present invention, in step (4), the inert atmosphere is one of nitrogen, argon, and helium.

[0021] According to some embodiments of the present invention, in step (4), the temperature of the heat treatment is 500 - 750 °C, and the time is 1 - 6 hours.

[0022] In the second aspect of the present invention, the present invention provides a magnetic titanium dioxide material. According to embodiments of the present invention, the magnetic titanium dioxide material is prepared by the above method. Thereby, the magnetic titanium dioxide material is a pure magnetic titanium dioxide material, that is, it is not doped with other magnetic elements nor compounded with other magnetic materials, has good stability, and its magnetism is easy to regulate, and has great application prospects in multiple industrial fields such as information, electronics, medicine, automobiles, power tools, and household appliances.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0025] Figure 1 is a schematic flow chart of a method for preparing a magnetic titanium dioxide material according to an embodiment of the present invention;

[0026] Figure 2 is an SEM image of the magnetic titanium dioxide material prepared in Example 1;

[0027] Figure 3 is a hysteresis loop diagram of the magnetic titanium dioxide material prepared in Example 1;

[0028] Figure 4 is a hysteresis loop diagram of the magnetic titanium dioxide material prepared in Example 2;

[0029] Figure 5 is a hysteresis loop diagram of the non-magnetic TiO2{001}-{101} facet heterojunction material prepared in Comparative Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0031] In the first aspect of the present invention, the present invention provides a method for preparing a magnetic titanium dioxide material. According to an embodiment of the present invention, with reference to Figure 1 , the method includes:

[0032] S100: Mix tetrabutyl titanate with a fluoride ion-containing solution

[0033] In this step, while stirring, tetrabutyl titanate is mixed with the fluoride ion-containing solution to obtain a mixed solution. Among them, the stirring time can be 25 to 35 minutes, preferably 30 minutes.

[0034] It should be noted that those skilled in the art can select the specific type of the fluoride ion-containing solution according to actual needs as long as it can provide fluoride ions. For example, the above-mentioned fluoride ion-containing solution includes but is not limited to hydrofluoric acid or sodium fluoride, and the fluoride ion concentration in the fluoride ion-containing solution is 15 to 25 mol / L. At the same time, the volume ratio of tetrabutyl titanate to the fluoride ion-containing solution is 25:(0 to 15), excluding the endpoint 0. The inventor found that as the addition amount of the fluoride ion-containing solution increases, the proportion of the {001} crystal plane in the subsequent obtained TiO2 heterojunction increases. However, too high a proportion of the {001} crystal plane will increase the risk of the experiment.

[0035] S200: Hydrothermally react the mixed solution and then perform solid-liquid separation

[0036] In this step, by hydrothermally reacting the mixed solution, F - adsorption can effectively reduce the surface energy of the {001} crystal plane, making it slightly lower than the surface energy of the {101} plane, and generating a TiO2 {001}-{101} crystal plane heterojunction with different proportions of the {001} and {101} crystal planes, which precipitates from the solution in the form of a white precipitate. Then, solid-liquid separation is performed on the reaction solution to obtain waste liquid and a white precipitate containing the TiO2 {001}-{101} crystal plane heterojunction. Specifically, the above hydrothermal reaction process can be carried out in a high-temperature and high-pressure hydrothermal reaction kettle. Further, the temperature of the above hydrothermal reaction is 160 to 200 °C, and the time is 20 to 36 hours. The inventor found that if the temperature of the hydrothermal reaction is too low, nucleation is not easy, complete crystallization is not easy, and there are many impurities; if the temperature of the hydrothermal reaction is too high, the particle size is too large, the specific surface area is small, and the air pressure is too high at too high a temperature, there are great potential safety hazards; at the same time, if the time of the hydrothermal reaction is too short, the product is less; if the time of the hydrothermal reaction is too long, the particle size increases and agglomeration is easy to form. It should be noted that the above solid-liquid separation process is a conventional technology in the art and will not be elaborated here.

[0037] S300: Wash and dry the white precipitate

[0038] In this step, the TiO₂ {001}-{101} facet heterojunction can be obtained by washing and drying the white precipitate containing the TiO₂ {001}-{101} facet heterojunction. Further, the above washing is carried out successively with absolute ethanol and water, so as to effectively remove the F - ions adsorbed on the surface of the sample. Thereby, the introduction of impurities during the subsequent heat treatment process can be avoided. Preferably, the white precipitate is washed three times successively with absolute ethanol and water. Thereby, the washing is carried out more thoroughly. It should be noted that the specific method of the above drying is not particularly limited, and those skilled in the art can choose according to actual needs. For example, drying can be carried out at 75-85 °C, preferably 80 °C.

[0039] S400: Heat-treat the TiO₂ {001}-{101} facet heterojunction in an inert atmosphere

[0040] In this step, in an inert atmosphere, the obtained TiO₂ {001}-{101} facet heterojunction is heat-treated, oxygen vacancies are introduced into the TiO₂ {001}-{101} facet heterojunction. After the introduction of oxygen vacancies, the internal electron distribution of the material changes, and the orbital electron spin magnetic moment also changes accordingly, making the material ferromagnetic; due to the differences in the Ti-O bond angles and binding energies of the {001} and {101} facets, there is a relationship between the oxygen vacancy formation energy and the facet ratio. Therefore, the magnetism of the material is induced by the synergistic regulation of the facets and oxygen vacancy defects, and a magnetic titanium dioxide material can be obtained. It should be noted that the specific type of the above inert atmosphere is not particularly limited, and those skilled in the art can choose according to actual needs. For example, the inert atmosphere includes but is not limited to nitrogen, argon or helium. Further, the temperature of the above heat treatment is 500-750 °C, and the time is 1-6 hours. The inventors found that if the heat treatment temperature is too low, it is not easy to form oxygen vacancies and it is not easy to remove the residual F ions on the surface of the sample; while if the heat treatment temperature is too high, a phase change will occur and the crystal structure will be changed. The time has little effect on the magnetism, but if the heat treatment time is too short, the oxygen vacancy concentration is low and the residual F ions on the surface cannot be removed cleanly; while if the heat treatment time is too long, agglomeration may occur and energy is wasted.

[0041] The inventors found that by mixing tetrabutyl titanate with a fluoride ion-containing solution and subjecting the obtained mixed solution to a hydrothermal reaction, F -Adsorption can effectively reduce the surface energy of the {001} crystal plane, making it slightly lower than that of the {101} plane. The generated TiO2 {001}-{101} crystal plane heterojunction precipitates from the solution in the form of a white precipitate. Then, solid-liquid separation is performed on the reaction solution to obtain the white precipitate and waste liquid. After washing and drying the white precipitate, the TiO2 {001}-{101} crystal plane heterojunction can be obtained. Finally, in an inert atmosphere, the TiO2 {001}-{101} crystal plane heterojunction is heat-treated, oxygen vacancies are introduced into the TiO2 {001}-{101} crystal plane heterojunction, and the magnetism of the material is induced through the synergistic regulation of the crystal plane and oxygen vacancy defects, and a magnetic titanium dioxide material can be obtained. Thus, the method of this application can be used to prepare a pure magnetic titanium dioxide material, that is, without doping other magnetic elements or being compounded with other magnetic materials. The prepared pure magnetic titanium dioxide material has good stability, and the magnitude of the magnetism can be adjusted by regulating the mixing ratio of tetrabutyl titanate and the fluoride ion solution, and then regulating the ratio of the {001} crystal plane. At the same time, this method is simple to operate, energy-saving and emission-reducing, and has low cost, suitable for mass production.

[0042] In the second aspect of the present invention, the present invention proposes a magnetic titanium dioxide material. According to the embodiments of the present invention, the magnetic titanium dioxide material is prepared by the above method. Thus, the magnetic titanium dioxide material is a pure magnetic titanium dioxide material, that is, without doping other magnetic elements or being compounded with other magnetic materials, has good stability, and the magnetism is easy to regulate, and has great application prospects in many industrial fields such as information, electronics, medicine, automobiles, power tools, and household appliances. It should be noted that the features and advantages described above for the method of preparing the magnetic titanium dioxide material also apply to this magnetic titanium dioxide material, and will not be repeated here.

[0043] The embodiments of the present invention are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention and cannot be understood as a limitation of the present invention. In addition, if not specified otherwise, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described in this article or known methods. For the reaction conditions not listed, they are also easily obtained by those skilled in the art.

[0044] Example 1

[0045] (1) Mix 25 mL of tetrabutyl titanate with 3 mL of hydrofluoric acid (fluoride ion concentration is 23 mol / L), and stir for half an hour to obtain a mixed solution;

[0046] (2) Transfer the mixed solution obtained in step (1) to a 100 mL hydrothermal reaction kettle, heat-treat at 180 °C for 24 hours, and filter to obtain a white precipitate;

[0047] (3) Wash the white precipitate obtained in step (2) three times with absolute ethanol and deionized water successively, and dry it at 80 °C to obtain the TiO₂ {001}-{101} crystal plane heterojunction;

[0048] (4) Heat-treat the TiO₂ {001}-{101} crystal plane heterojunction obtained in step (3) in a nitrogen atmosphere at 550 °C for 2 hours to obtain the magnetic TiO₂ {001}-{101} crystal plane heterojunction material. The scanning electron microscope image of this material is as Figure 2 shown, Figure 3 and the hysteresis loop diagram of this sample is given. It can be seen from its XRD spectrum that the magnetic TiO₂ {001}-{101} crystal plane heterojunction material is a pure magnetic titanium dioxide material, that is, no other magnetic elements are doped and no other magnetic materials are compounded.

[0049] Example 2

[0050] (1) Mix 25 mL of tetrabutyl titanate with 4.5 mL of hydrofluoric acid (fluoride ion concentration is 23 mol / L), and stir for half an hour to obtain a mixed solution;

[0051] (2) Transfer the mixed solution obtained in step (1) to a 100 mL hydrothermal reaction kettle, heat-treat it at 180 °C for 24 hours, and filter to obtain a white precipitate;

[0052] (3) Wash the white precipitate obtained in step (2) three times with absolute ethanol and deionized water successively, and dry it at 80 °C to obtain the TiO₂ {001}-{101} crystal plane heterojunction;

[0053] (4) Heat-treat the TiO₂ {001}-{101} crystal plane heterojunction obtained in step (3) in a nitrogen atmosphere at 550 °C for 2 hours to obtain the magnetic TiO₂ {001}-{101} crystal plane heterojunction material, Figure 4 and the hysteresis loop diagram of this sample is given. It can be seen from its XRD spectrum that the magnetic TiO₂ {001}-{101} crystal plane heterojunction material is a pure magnetic titanium dioxide material, that is, no other magnetic elements are doped and no other magnetic materials are compounded.

[0054] Example 3

[0055] (1) Mix 25 mL of tetrabutyl titanate with 9 mL of hydrofluoric acid (fluoride ion concentration is 23 mol / L), and stir for half an hour to obtain a mixed solution;

[0056] (2) Transfer the mixed solution obtained in step (1) to a 100 mL hydrothermal reaction kettle, heat-treat it at 180 °C for 24 hours to obtain a white precipitate;

[0057] (3) Wash the white precipitate obtained in step (2) three times with absolute ethanol and deionized water successively, and dry it at 80 °C to obtain a TiO2 {001}-{101} facet heterojunction.

[0058] (4) Heat-treat the TiO2 {001}-{101} facet heterojunction obtained in step (3) in a nitrogen atmosphere at 550 °C for 2 hours to obtain a magnetic TiO2 {001}-{101} facet heterojunction material. From its hysteresis loop diagram, it can be seen that this magnetic TiO2 {001}-{101} facet heterojunction material has strong magnetism. From its XRD spectrum, it can be seen that the magnetic TiO2 {001}-{101} facet heterojunction material is a pure magnetic titanium dioxide material, that is, it is not doped with other magnetic elements and is not composite with other magnetic materials.

[0059] Comparative Example 1

[0060] (1) Add 25 mL of tetrabutyl titanate to a 100 mL hydrothermal reaction kettle, and heat-treat it at 180 °C for 24 hours to obtain a white precipitate.

[0061] (2) Wash the white precipitate obtained in step (1) three times with absolute ethanol and deionized water successively, and dry it at 80 °C to obtain TiO2.

[0062] (3) Heat-treat the TiO2 obtained in step (2) in a nitrogen atmosphere at 550 °C for 2 hours to obtain a non-magnetic material.

[0063] Comparative Example 2

[0064] (1) Mix 25 mL of tetrabutyl titanate with 3 mL of hydrofluoric acid (fluoride ion concentration is 25 mol / L), and stir for half an hour to obtain a mixed solution.

[0065] (2) Transfer the mixed solution obtained in step (1) to a 100 mL hydrothermal reaction kettle, and heat-treat it at 180 °C for 24 hours to obtain a white precipitate.

[0066] (3) Wash the white precipitate obtained in step (2) three times with absolute ethanol and deionized water successively, and dry it at 80 °C to obtain a TiO2 {001}-{101} facet heterojunction.

[0067] (4) Heat-treat the TiO2 {001}-{101} facet heterojunction obtained in step (3) in an air atmosphere at 550 °C for 2 hours to obtain a non-magnetic TiO2 {001}-{101} facet heterojunction material. Figure 5 The hysteresis loop diagram of this sample is given.

[0068] In the description of this specification, the descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0069] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing ferromagnetic titanium dioxide material, characterized in that, Including: (1) Mix 25 mL of tetrabutyl titanate with 4.5 mL of hydrofluoric acid and stir for half an hour to obtain a mixed solution, where the fluoride ion concentration of hydrofluoric acid is 23 mol / L; (2) Transfer the mixed solution obtained in step (1) to a 100 mL hydrothermal reactor, heat-treat at 180 °C for 24 hours, and obtain a white precipitate after filtration; (3) Wash the white precipitate prepared in step (2) three times with anhydrous ethanol and deionized water successively, and dry at 80 °C to prepare a TiO2{001}-{101} crystal plane heterojunction; (4) Heat-treat the TiO2{001}-{101} crystal plane heterojunction obtained in step (3) in a nitrogen atmosphere at 550 °C for 2 hours to obtain a magnetic TiO2{001}-{101} crystal plane heterojunction material.

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