Method for preparing TiO2 nano-powder with controllable phase

Abstract

The invention discloses a phase-controllable method for preparing TiO2 nano powder, and relates to the technical field of nano material preparation. Industrial titanium-containing powder and water are used as raw materials, hydrochloric acid and sodium nitrate are added to serve as an acid medium and an additive respectively, and TiO2 nano-powder with the anatase phase and the rodlike morphology is prepared through a solvothermal reaction. Industrial titanium-containing powder and water are used as raw materials, nitric acid and sodium chloride are added to serve as an acid medium and an additive respectively, and the TiO2 nano-powder with the rutile phase and the rodlike morphology is prepared through solvothermal reaction. According to the invention, the rod-like TiO2 nano powder can be prepared by carrying out solvothermal reaction on the titanium-containing industrial powder in the mixed acid for the first time, and the reaction mechanism is disclosed. And meanwhile, by reasonably selecting the combination of the acidic medium and the additive and reasonably adjusting the concentration of the acidic medium, controllable preparation of different phases of TiO2 nano powder is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-material preparation, and particularly to a method for controllably preparing TiO2 nano-powders with adjustable phases. Background Art

[0002] Research shows that one-dimensional TiO2 (mainly including nanowires, nanorods, nanotubes, etc.) has a high specific surface area and refractive index (n~2.7), and can effectively reflect and scatter ultraviolet light, making it the preferred material for high-quality white pigments and optical coatings. In addition, anatase-phase TiO2 has slightly better photocatalytic activity than rutile-phase TiO2, and is widely used in photocatalytic sewage treatment, solar cell construction, and materials for new energy vehicles.

[0003] For the preparation of TiO2 nano-powders, industrially, titanium tetrachloride (TiCl4) is usually used as the raw material to produce anatase-type TiO2 nano-powders. Although this method has a large output, it requires special equipment, and the phase and morphology of the product are uncontrollable. In addition, tetrabutyl titanate is used as the titanium source, and sol-gel method or hydrothermal method is adopted to prepare various forms of TiO2 nano-materials, but the raw materials required by this method are expensive and the cost is high.

[0004] Metatitanic acid (H2TiO3), titanium nitride (TiN), titanium carbide (TiC), titanium carbonitride (TiCN), and other titanium-containing solid substances are all common industrial raw materials. Among them, TiN, or TiC and TiCN powders are the main raw materials for producing cemented carbides or cermets. The present invention takes these titanium-containing industrial raw materials as the research object, adopts an acid synthesis method to controllably prepare high-quality TiO2 nano-powders, and can realize the phase regulation of anatase-type and rutile-type products. At the same time, this method has the characteristics of simple operation, low cost, high product quality and excellent performance, and can be used in the actual production field. Summary of the Invention

[0005] In order to solve the above deficiencies existing in the existing TiO2 nano-powder preparation process, the present invention aims to propose a method for controllably preparing TiO2 nano-powders, which can realize the dual controllable adjustment of morphology and phase.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for controllably preparing TiO2 nano-powders with a specific phase. Using industrial titanium-containing powders and water as raw materials, hydrochloric acid and sodium nitrate are added as an acidic medium and an additive respectively, and TiO2 nano-powders with anatase phase and rod-like morphology are prepared through a solvothermal reaction; using industrial titanium-containing powders and water as raw materials, nitric acid and sodium chloride are added as an acidic medium and an additive respectively, and TiO2 nano-powders with rutile phase and rod-like morphology are prepared through a solvothermal reaction.

[0008] As a preferred technical solution of the present invention, the industrial titanium-containing powders in the preparation method are selected from one or a combination of more of metatitanic acid (H2TiO3), titanium nitride (TiN), titanium carbide (TiC), and titanium carbonitride (TiCN).

[0009] As a preferred technical solution of the present invention, the addition amount of hydrochloric acid used for preparing anatase TiO2 nano-powders is 100 - 150 times the mass of the industrial titanium-containing powders, the addition amount of sodium nitrate used is 15 wt% - 25 wt% of the mass of the industrial titanium-containing powders, and the addition amount of water used is 3 - 5 times the volume of hydrochloric acid.

[0010] As a preferred technical solution of the present invention, the addition amount of nitric acid used for preparing rutile TiO2 nano-powders is 10 - 15 times the mass of the industrial titanium-containing powders, the addition amount of sodium chloride used is 15 wt% - 25 wt% of the mass of the industrial titanium-containing powders, and the addition amount of water used is 30 - 50 times the volume of nitric acid.

[0011] As a preferred technical solution of the present invention, the solvothermal reaction temperature in the preparation method is 140 °C - 200 °C, and the reaction time is 10 h - 36 h.

[0012] As a preferred technical solution of the present invention, after the solvothermal reaction is complete in the preparation method, the reactants are taken out, the acidic medium is filtered out by a membrane, and then washed with deionized water and ethanol in sequence and dried.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] 1. The present invention proposes a method for controllably preparing TiO2 nano-powders with a specific phase, which can achieve high-quality TiO2 nano-powders and can also achieve controllable adjustment of morphology and phase.

[0015] 2. The metatitanic acid (H2TiO3), titanium nitride (TiN), titanium carbide (TiC), and titanium carbonitride (TiCN) used in the present invention are more widely sourced and novel compared to traditional preparation methods. The present invention first proposed that rod-shaped TiO2 nanometer powder can be prepared by solvothermal reaction of titanium-containing industrial powder in mixed acid, and revealed the reaction mechanism. At the same time, by reasonably selecting the combination of acidic medium and additives and reasonably adjusting the concentration of the acidic medium, the controllable preparation of TiO2 nanometer powder with different phases was achieved.

[0016] 3. The band gap value of the TiO2 nanorod material prepared in the present invention is about 3.3 eV, which is basically consistent with the theoretically calculated band gap value. Since the band gap of TiO2 is a key parameter determining its photocatalytic, photovoltaic, and photoelectrochemical properties, the TiO2 nanorod material prepared in the present invention has high application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 SEM images (a) and XRD patterns (b) of the TiO2 nanomaterial prepared in Example 1.

[0018] Figure 2 SEM images (a) and XRD patterns (b) of the TiO2 nanomaterial prepared in Example 2.

[0019] Figure 3 SEM images (a) and XRD patterns (b) of the TiO2 nanomaterial prepared in Comparative Example 1.

[0020] Figure 4 SEM images (a) and XRD patterns (b) of the TiO2 nanomaterial prepared in Comparative Example 2.

[0021] Figure 5 SEM images (a) and XRD patterns (b) of the TiO2 nanomaterial prepared in Comparative Example 3.

[0022] Figure 6 SEM images (a) and XRD patterns (b) of the TiO2 nanomaterial prepared in Comparative Example 4.

[0023] Figure 7 BET curves of the TiO2 nanomaterials prepared in Examples 1 and 2.

[0024] Figure 8 Energy band structures (a) and optical band gap curves (b) of the TiO2 nanomaterials prepared in Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention provides a method for controllably preparing TiO2 nano-powders. Using industrial titanium-containing powders and water as raw materials, hydrochloric acid and sodium nitrate are added as an acidic medium and an additive respectively, and anatase-type TiO2 nano-powders with a rod-like morphology are prepared through a solvothermal reaction; alternatively, using industrial titanium-containing powders and water as raw materials, nitric acid and sodium chloride are added as an acidic medium and an additive respectively, and rutile-type TiO2 nano-powders with a rod-like morphology are prepared through a solvothermal reaction.

[0026] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The phase, morphology, and light absorption properties of the target product in the embodiments are characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (SU8010), and ultraviolet-visible spectrometer (UV) respectively.

[0027] Example 1: Controllable preparation and characterization of anatase-type TiO2 nanorods

[0028] Take 50 mg of H2TiO3 powder and put it into a clean beaker. Add 5 mL of 37% concentrated hydrochloric acid and 20 mL of deionized water thereto. After ultrasonic dispersion, add 10 mg of NaNO3 and stir to mix evenly. Transfer the above mixture into a reaction kettle, seal it, and heat it in an oven at 180 °C for 24 h. After the reaction is completed, filter out the acidic medium of the product by membrane, and perform multiple washings (deionized water, ethanol) and drying treatments to obtain the target powder.

[0029] As shown in Figure 1 a, the morphology of the product prepared in Example 1 is a rod-like structure. Figure 1 b is the XRD pattern of the product. After comparison with the standard XRD pattern of anatase-type TiO2, it can be seen that the phase of the product obtained under this process is anatase-type. As shown in Figure 7 it can be seen that the specific surface area of this TiO2 nanomaterial reaches 103 m 2 / g.

[0030] Equation (1) is the reaction roadmap of Example 1. Under this reaction condition, the formation mechanism of anatase-type TiO2 nanorods can be explained as follows: First, solid H2TiO3 dissolves in the mixed acid root ion solution (NO3 - , Cl - ) to form Ti 4+ . Then, supersaturated Ti 4+ in the liquid phase forms TiO2 particles through recrystallization. Finally, the TiO2 particles self-assemble to form anatase-type TiO2 nanorods under the mixed acid vapor pressure.

[0031]

[0032] Example 2: Controllable Preparation and Characterization of Rutile TiO₂ Nanorods

[0033] Take 50 mg of TiN powder and put it into a clean beaker. Add 0.5 mL of 68% concentrated nitric acid and 20 mL of deionized water to it. After ultrasonic dispersion, add 10 mg of NaCl and stir to mix evenly. Transfer the above mixture into a reaction kettle, seal it, and heat it in an oven at 180 °C for 24 h. After the reaction is completed, filter out the acidic medium of the product by membrane filtration, and carry out multiple washings (deionized water, ethanol) and drying treatments to obtain the target powder.

[0034] As can be seen from Figure 2 a, the morphology of the product prepared in Example 2 is a rod-like structure. Figure 2 b is the XRD pattern of the product. By comparing it with the standard XRD pattern of rutile TiO₂, it can be seen that the phase of the product obtained under this process is rutile. As can be seen from Figure 7 it can be seen that the specific surface area of this TiO₂ nanomaterial reaches 128 m 2 / g.

[0035] Equation (2) is the reaction roadmap of Example 2. Under this reaction condition, the formation mechanism of rutile TiO₂ nanorods can be explained as follows: First, solid TiN dissolves in the mixed acid root ion solution (NO₃ - , Cl - ) to form Ti 4+ . Then, supersaturated Ti 4+ in the liquid phase forms TiO₂ particles by recrystallization. Finally, the TiO₂ particles self-assemble to form rutile TiO₂ nanorods under the pressure of the mixed acid vapor.

[0036]

[0037] Comparative Example 1

[0038] In this comparative example, in order to verify the influence of different acidic media participating in the reaction on the prepared product, concentrated hydrochloric acid in the preparation process of Example 1 was replaced with concentrated nitric acid.

[0039] As can be seen from Figure 3 a, the morphology of the product prepared in Comparative Example 1 is an irregular granular structure. Figure 3 b is the XRD pattern of the product. It can be seen from the figure that there are many miscellaneous items in the product and the purity is not high.

[0040] Comparative Example 2

[0041] In this comparative example, in order to verify the influence of different acidic media participating in the reaction on the prepared product, concentrated nitric acid in the preparation process of Example 2 was replaced with concentrated hydrochloric acid.

[0042] As can be seen from Figure 4As can be seen from a, the morphology of the product prepared in Comparative Example 2 also shows an irregular granular structure. Figure 4 b is the XRD pattern of the product. As can be seen from the figure, there are many miscellaneous items in the product and the purity is not high.

[0043] Comparative Example 3

[0044] In this comparative example, in order to verify the influence of different concentrations of acidic media on the prepared product, the volume of concentrated hydrochloric acid in the preparation process of Example 1 was adjusted to 0.5 mL.

[0045] From Figure 5 a, it can be seen that the morphology of the product prepared in Comparative Example 3 also shows an irregular granular structure. Figure 5 b is the XRD pattern of the product. As can be seen from the figure, the product has both anatase type and rutile type.

[0046] Comparative Example 4

[0047] In this comparative example, in order to verify the influence of different concentrations of acidic media on the prepared product, the volume of concentrated nitric acid in the preparation process of Example 2 was adjusted to 5 mL.

[0048] From Figure 6 a, it can be seen that the morphology of the product prepared in Comparative Example 4 also shows an irregular granular structure. Figure 6 b is the XRD pattern of the product. As can be seen from the figure, the product has both anatase type and rutile type, and the purity is low and there are many miscellaneous peaks.

[0049] Combining Example 1, 2 and Comparative Examples 1, 2, 3, 4, it can be seen that the present invention realizes the controllable preparation of TiO2 nano-powders with different phases by reasonably selecting the combination of acidic media and additives and reasonably adjusting the concentration of acidic media.

[0050] Example 3: Comparison of the light absorption properties of anatase type and rutile type TiO2

[0051] Rutile type TiO2 is a direct bandgap semiconductor, while anatase type TiO2 is an indirect bandgap semiconductor. The bandgap of TiO2 is a key parameter determining its photocatalytic, photovoltaic and photoelectrochemical properties. Theoretical calculations play an important role in predicting and explaining the bandgap of TiO2.

[0052] The energy band structure of TiO2 was calculated using the Heyd-Scuserna-Ernzerhof (HSE06) functional, and the results are as Figure 4 shown in a. From Figure 4It can be seen that the theoretical calculated band gap value of rutile TiO2 is about 3.3 eV, and the experimental value is about 3.3 eV, showing consistency between the two. For anatase TiO2, its theoretical calculated band gap is about 3.0 eV, while the experimental value is about 2.7 eV. The reason for the large difference between the two is that the experimental value is calculated according to the direct band gap (E g = 1240 / λ max ), resulting in a large error.

[0053] The above content is only an example and explanation of the concept of the present invention. Those skilled in the art of the present technology can make various modifications, supplements, or use similar methods to replace the specific embodiments described. As long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

Claims

1. A method for controllably preparing TiO2 nano-powders in terms of phase, characterized in that, Using industrial titanium-containing powder and water as raw materials, hydrochloric acid and sodium nitrate are added as acidic medium and additive respectively, and TiO2 nano-powder with anatase phase and rod-like morphology is prepared by solvothermal reaction; using industrial titanium-containing powder and water as raw materials, nitric acid and sodium chloride are added as acidic medium and additive respectively, and TiO2 nano-powder with rutile phase and rod-like morphology is prepared by solvothermal reaction.

2. The method according to claim 1, characterized in that, The industrial titanium-containing powder is selected from one or more combinations of metatitanic acid (H2TiO3), titanium nitride (TiN), titanium carbide (TiC), and titanium carbonitride (TiCN).

3. The method according to claim 1, wherein, The addition amount of hydrochloric acid used to prepare anatase TiO2 nano-powder is 100 - 150 times the mass of the industrial titanium-containing powder, the addition amount of sodium nitrate used is 15 wt% - 25 wt% of the mass of the industrial titanium-containing powder, and the addition amount of water used is 3 - 5 times the volume of hydrochloric acid.

4. The method according to claim 1, wherein The addition amount of nitric acid used to prepare rutile TiO2 nano-powder is 10 - 15 times the mass of the industrial titanium-containing powder, the addition amount of sodium chloride used is 15wt% - 25 wt% of the mass of the industrial titanium-containing powder, and the addition amount of water used is 30 - 50 times the volume of nitric acid.

5. The method according to claim 1, wherein The solvothermal reaction temperature is 140 °C - 200 °C, and the reaction time is 10 h - 36 h.

6. The method according to any one of claims 1 to 5, characterized in that After the solvothermal reaction is complete, the reactants are taken out, the acidic medium is filtered out by a membrane, and then washed and dried with deionized water and ethanol in sequence.

7. TiO2 nano-powder prepared by the method according to any one of claims 1 - 6.

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