A method for growing a layer of titania nanorod crystals in situ on a titania ceramic surface

Abstract

The application relates to a method for growing a titanium dioxide nanorod crystal layer in situ on a titanium dioxide ceramic surface. The method comprises the following steps: (1) applying titanium powder on a titanium dioxide ceramic surface, or dispersing titanium powder in a solvent to form a titanium powder dispersion liquid, and then applying the titanium powder dispersion liquid on the titanium dioxide ceramic surface, and after drying, obtaining a titanium dioxide ceramic coated with titanium powder on the surface; (2) heat-treating the titanium dioxide ceramic coated with titanium powder on the surface under certain conditions, so that the surface of the titanium dioxide ceramic is subjected to lattice distortion; removing the titanium powder layer on the surface of the titanium dioxide ceramic after reaction; and (3) growing a titanium dioxide nanorod crystal layer in situ on the surface of the titanium dioxide ceramic subjected to lattice distortion through a hydrothermal reaction.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of titanium dioxide materials, and relates to a method for growing a titanium dioxide nanorod crystal layer in situ on a titanium dioxide ceramic surface. BACKGROUND

[0002] The titanium dioxide nanorod crystal layer with a nano-ordered array structure has a wide application prospect in the fields of photocatalysis, seawater desalination, sewage treatment, etc. due to its direct electron transmission channel, large specific surface area, good corrosion resistance and oxidation resistance, etc.

[0003] Common methods for preparing the titanium dioxide nanorod crystal layer mainly include hydrothermal synthesis, electrospinning, titanium substrate anodic oxidation, template method and chemical vapor deposition, etc. The hydrothermal synthesis method has the advantages of simple process, simple condition control, low cost and no need for a template for direct in-situ growth.

[0004] The existing hydrothermal synthesis of the titanium dioxide nanorod crystal layer uses substrates such as titanium sheets [1] , titanium layers [2] after oxidation treatment and FTO conductive glass [3] , etc. However, the strength and stability of these substrates are not enough, which greatly limits the application field of the titanium dioxide nanorod crystal layer, and therefore, it is urgent to find new substrates for preparing the titanium dioxide nanorod crystal layer.

[0005] The high strength, high weather resistance and adjustable pore structure inherent in the titanium dioxide ceramic as a ceramic material mean that it has a more extensive application prospect in fields such as seawater desalination, sewage treatment, etc. compared to other existing substrate materials. However, the titanium dioxide ceramic surface lacks active growth sites and is not lattice-matched with the titanium dioxide nanorod crystal layer, and therefore, it cannot directly grow the titanium dioxide nanorod crystal layer by the hydrothermal synthesis method.

[0006] REFERENCES

[0007] [1] Cai J, Ye J, Chen S, et al. Self-cleaning, broadband and quasi-omnidirectional antireflective structures based on mesocrystalline rutile TiO2 nanorod arrays [J]. Energy & Environmental Science, 2012, 5(6): 7575-7581.

[0008] [2] Jaffari GH, Hussain T, Iqbal AM, Abbas Y. Formation and crystallization of TiO2 nanostructures on various surfaces. Acta Crystallogr B Struct Sci Cryst Eng Mater. 2022 Aug 1;78(Pt 4):593-605. [3] Wu W Q, Lei B X, Rao HS, et al. Hydrothermal Fabrication of Hierarchically Anatase TiO2 Nanowire arrays on FTO Glass for Dye-sensitized Solar Cells [J]. Scientific Reports, 2013, 3: 1352. SUMMARY

[0009] To solve the above problems, the application provides a method for growing a titanium dioxide nanorod crystal layer in situ on the surface of a titanium dioxide ceramic.

[0010] In one aspect, the application provides a method for growing a titanium dioxide nanorod crystal layer in situ on the surface of a titanium dioxide ceramic, comprising the following steps:

[0011] (1) applying titanium powder to the surface of a titanium dioxide ceramic, or dispersing titanium powder in a solvent to form a titanium powder dispersion, and then applying the titanium powder dispersion to the surface of a titanium dioxide ceramic, and drying to obtain a titanium dioxide ceramic with a titanium powder coating on the surface;

[0012] (2) heat treating the titanium dioxide ceramic with a titanium powder coating on the surface under certain conditions to cause lattice distortion on the surface of the titanium dioxide ceramic; and removing the titanium powder layer on the surface of the titanium dioxide ceramic after the reaction;

[0013] (3) growing a titanium dioxide nanorod crystal layer in situ on the surface of the titanium dioxide ceramic with lattice distortion through a hydrothermal reaction.

[0014] The application realizes the change of the titanium dioxide ceramic surface lattice by coating titanium powder on the surface of the titanium dioxide ceramic and performing heat treatment, and provides active growth sites for the growth of titanium dioxide nanorods after the titanium powder layer naturally falls off, so that it is possible to grow a titanium dioxide nanorod crystal layer on the titanium dioxide ceramic surface in situ, and compared with the existing substrate material, the titanium dioxide ceramic has high strength, high weather resistance and adjustable pore structure, and the combination with the titanium dioxide nanorod crystal layer grown on the surface in situ is more close, which is more conducive to widening the application in the fields of photocatalysis, seawater desalination, sewage treatment and the like.

[0015] Preferably, in step (1), the amount of titanium powder applied on the surface of the titanium dioxide ceramic is 0.0008-0.02 g / cm 2 .

[0016] Preferably, in step (1), the solvent of the titanium powder dispersion liquid is ethanol or deionized water; and the concentration of the titanium powder dispersion liquid is 5-15 mol / L.

[0017] Preferably, in step (2), the parameters of the heat treatment include: the temperature of the heat treatment is 500-1050℃, the holding time is 0.5-8 h, the heating rate is 2-10℃ / min, and the environmental atmosphere is vacuum or inert gas atmosphere; preferably, the temperature of the heat treatment is 800-900℃, the holding time is 0.5-3 h, and the environmental atmosphere is vacuum or inert gas atmosphere.

[0018] Preferably, in step (2), after the heat treatment, the composition of the titanium powder layer after the surface reaction includes: titanium powder and titanium oxide.

[0019] Preferably, in step (3), the hydrothermal reaction includes: first, a mixed solution is prepared by mixing tetrabutyl titanate, hydrochloric acid and deionized water, then the titanium dioxide ceramic with the surface lattice distortion is put into the mixed solution to perform hydrothermal reaction in a hydrothermal reaction kettle, so as to obtain a titanium dioxide nanorod crystal layer grown on the surface of the titanium dioxide ceramic in situ.

[0020] Preferably, the temperature of the hydrothermal reaction is 120-180℃, and the time is 4-20 h.

[0021] Preferably, the volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water in the mixed solution is 1:10-30:10-30.

[0022] The concentration of the hydrochloric acid is 36-38%.

[0023] Preferably, in step (2), the titanium powder layer after the surface reaction of the titanium dioxide ceramic is removed by purging or cleaning.

[0024] Beneficial effects:

[0025] (1) Compared with the prior art, the titanium dioxide nanorod crystal layer can be directly grown in situ on the surface of the titanium dioxide ceramic.

[0026] (2) The titanium dioxide nanorod crystal layer prepared by the application has an ordered layered array structure, is uniform and stable, has high bonding strength, large specific surface area, and excellent corrosion resistance and oxidation resistance, and can be widely applied in the fields of photocatalysis, seawater desalination, sewage treatment and the like. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM pictures of the titanium powder layer on the surface of the titanium dioxide ceramic after heat treatment and the titanium dioxide ceramic with lattice distortion on the surface;

[0028] Figure 2 Actual pictures of the titanium powder layer on the surface of the titanium dioxide ceramic after heat treatment and the titanium dioxide ceramic with lattice distortion on the surface;

[0029] Figure 3 XRD results of the titanium powder layer on the surface of the titanium dioxide ceramic after heat treatment and the titanium dioxide ceramic with lattice distortion on the surface;

[0030] Figure 4 (a) and (b) are SEM pictures of the titanium powder; (c) and (d) are SEM pictures of the titanium powder layer on the surface of the titanium dioxide ceramic after heat treatment (the magnification is ×100, ×2000, ×100 and ×2000, respectively);

[0031] Figure 5 XRD results of the titanium dioxide ceramic substrate and the titanium dioxide ceramic substrate with lattice distortion on the surface after heat reaction;

[0032] Figure 6 SEM pictures of the titanium dioxide ceramic (a) in Example 1 and the titanium dioxide ceramic with the titanium dioxide nanorod crystal layer grown in situ on the surface for 6h (b) (the magnification is ×3000 and 5000, respectively);

[0033] Figure 7 SEM picture of the titanium dioxide ceramic with the titanium dioxide nanorod crystal layer grown in situ on the surface for 13h in Example 2 (the magnification is ×3000);

[0034] Figure 8 SEM pictures of the titanium dioxide ceramic (a), the titanium dioxide ceramic with lattice distortion on the surface (b) and the titanium dioxide ceramic with the titanium dioxide nanorod crystal layer grown in situ on the surface (c) in Example 2 (the magnification is ×3000);

[0035] Figure 9SEM images (×3000 magnification) of the titanium dioxide ceramic (a), the titanium dioxide ceramic with lattice distortion on the surface (b) and the titanium dioxide ceramic after growing the titanium dioxide nanorod crystal layer in-situ on the surface (c) in Example 3;

[0036] Figure 10 SEM images (×3000 magnification) of the titanium dioxide ceramic (a), the titanium dioxide ceramic with lattice distortion on the surface (b) and the titanium dioxide ceramic after growing the titanium dioxide nanorod crystal layer in-situ on the surface (c) in Example 4; Figure 11 SEM images (×5000, ×4000 and ×8000 magnification) of the titanium dioxide ceramic after growing the titanium dioxide nanorod crystal layer in-situ on the surface in Example 2 (a), Example 3 (b) and Example 4 (c);

[0037] Figure 12 SEM image (×1000 magnification) of the titanium dioxide nanorod crystal layer grown by using the seed coating method in Comparative Example 1;

[0038] Figure 13 SEM image (×4000 magnification) of the titanium dioxide ceramic after the hydrothermal reaction in Comparative Example 2;

[0039] Figure 14 SEM image (×4000 magnification) of the titanium dioxide ceramic after the hydrothermal reaction in Comparative Example 3;

[0040] Figure 15 SEM image (×4000 magnification) of the titanium dioxide ceramic after the hydrothermal reaction in Comparative Example 4;

[0041] Figure 16 SEM images (×2000 and ×6000 magnification) of the titanium dioxide ceramic after the hydrothermal reaction in Comparative Example 5. DETAILED DESCRIPTION

[0042] To further illustrate the content, features and practical effects of the present application, the present application will be described in detail in conjunction with the examples. It should be noted that the modification method of the present application is not limited to these specific embodiments. Equivalent substitutions and modifications made by those skilled in the art on the basis of the content of the present application without departing from the spirit and content of the present application are also within the scope of the present application.

[0043] The present invention uses a brush coating or solvent dispersion method to coat titanium powder on the surface of a titanium dioxide ceramic. After heat treatment, the titanium powder layer after the surface reaction is removed to obtain a titanium dioxide ceramic with a lattice distortion on the surface. Finally, a titanium dioxide nanorod crystal layer is in situ grown on the surface of the titanium dioxide ceramic through a hydrothermal reaction. Under appropriate hydrothermal conditions, the method provided by the present invention can produce a uniform, stable, high-bonding-strength, and large-specific-surface-area titanium dioxide nanorod crystal layer on the surface of the titanium dioxide ceramic. The titanium dioxide nanorod crystal layer produced by the present invention has excellent corrosion resistance and antioxidant properties and can be widely used in industries such as photocatalysis, seawater desalination, and sewage treatment.

[0044] In the present invention, the purpose of coating titanium powder on the surface of titanium dioxide ceramics is to react with the TiO2 ceramic matrix to change the lattice of the titanium dioxide ceramic surface. Figures 1-2 As shown, under certain heat treatment conditions, the titanium powder reacts with the ceramic matrix. After the titanium powder layer falls off naturally after the surface reaction, it is found that the thermal reaction between the titanium powder and the titanium dioxide ceramic surface causes lattice distortion. These lattice distortions can serve as active growth sites for the growth of titanium dioxide nanorods. Under hydrothermal reaction conditions, a layer of titanium dioxide nanorod crystals can be grown in situ at these active growth sites on the titanium dioxide ceramic surface.

[0045] Specifically, the thermal reaction between the titanium powder coated on the surface of the titanium dioxide ceramic and the titanium dioxide ceramic substrate is a process in which the TiO2 lattice on the surface of the titanium dioxide ceramic substrate loses oxygen, and the titanium powder absorbs oxygen from the TiO2 lattice during the thermal reaction. After the reaction is completed, the titanium powder layer (including the oxygen-absorbing titanium oxide and the non-oxygen-absorbing titanium powder) is removed from the surface of the titanium dioxide ceramic substrate. The TiO2 lattice on the surface of the titanium dioxide ceramic substrate is in an oxygen-deficient state, that is, lattice distortion (or defects) occurs on the surface of the titanium dioxide ceramic substrate. The lattice distortion can serve as an active growth site for the titanium dioxide nanorod crystal layer, and the TiO2 nanorods can begin to grow from the lattice distortion.

[0046] In the present application, on the one hand, by controlling the thermal reaction of titanium powder and the surface of titanium dioxide ceramic, the active growth sites of titanium dioxide nanorod crystal layer are obtained. If the temperature of heat treatment is too high, the oxygen deficiency of TiO2 lattice on the surface of titanium dioxide ceramic substrate is too large, and the lattice defects are too many, which leads to lattice mismatch and the titanium dioxide nanorod cannot grow. If the temperature of heat treatment is too low, the TiO2 lattice on the surface of titanium dioxide ceramic substrate cannot be oxygen-deficient, and the lattice distortion cannot occur, so it is difficult to obtain active growth sites, and the titanium dioxide nanorod crystal layer cannot grow. On the other hand, by controlling the conditions of hydrothermal reaction, a suitable growth environment is provided for the in-situ growth of titanium dioxide nanorod. In the process, if the temperature of hydrothermal reaction is too low or the time is too short, the chemical driving force for the growth of titanium dioxide nanorod at the active sites will be insufficient, and the titanium dioxide nanorod crystal layer cannot grow. If the temperature of hydrothermal reaction is too high or the time is too long, the chemical driving force is too strong, and the titanium dioxide nanorod will grow rapidly, which will lead to the overfilling of the titanium dioxide nanorod on the surface of titanium dioxide ceramic, and the excessive densification, so that the nanorod crystal grown in-situ on the titanium dioxide ceramic loses the morphology characteristics of nanorod as a whole.

[0047] The following examples illustrate the method for growing a titanium dioxide nanorod crystal layer in-situ on the surface of titanium dioxide ceramic provided by the present application.

[0048] Preparation of TiO2 ceramic substrate. In the present invention, the TiO2 ceramic substrate can be prepared by dry pressing and sintering method (L. Chen, D. Yao, H. Liang, Y. Xia, Y.-P. Zeng, Highly stable TiO2 ceramics for high efficiency and practical solar-driven interfacial evaporation, Solar Energy, 262 (2023) 111848.), freeze drying and sintering method (L. Ren, Y.-P. Zeng, D. Jiang, Preparation of porous TiO2 by a novel freeze casting, Ceramics International, 35 (2009) 1267-1270.). As an example, the dry pressing and sintering method comprises: using TiO2 powder with particle size of 100-2000 nm as raw material, and the initial crystal phase is anatase. 40 g of TiO2 powder is dry pressed into a ceramic green body under a pressure of 20 MPa. Then the ceramic green body is placed in a muffle furnace and sintered at 1000-1250 °C for 0.5-5 h with a heating rate of 1-10 °C / min to obtain the TiO2 ceramic substrate. The freeze drying and sintering method: using TiO2 powder with particle size of 100-2000 nm as raw material, and the initial crystal phase is anatase. The TiO2 powder, ammonium polyacrylate, and polyvinyl alcohol are mixed in deionized water, wherein the ammonium polyacrylate is 1%-2% of the mass of the TiO2 powder, the polyvinyl alcohol is 1%-6% of the mass of the TiO2 powder, and the deionized water is 20%-80% of the mass of the TiO2 powder. The mixture is ball milled in a plastic bottle with zirconia balls as medium for 24 h to obtain a well-dispersed and stable slurry. The obtained slurry is degassed using a vacuum degassing machine, and then poured into a rectangular rubber mold. Subsequently, the rectangular rubber mold filled with the slurry is placed in a cold room with a temperature of -80 °C. After 10 h, the completely frozen sample is peeled off from the rectangular rubber mold and quickly transferred to the vacuum chamber of a freeze dryer. The frozen sample is dried in a low vacuum condition for 15 h. Due to the sublimation of ice crystals, a ceramic green body is obtained. Then the ceramic green body is sintered in a muffle furnace at 1000-1250 °C for 0.5-5 h with a heating rate of 1-5 °C / min to obtain the TiO2 ceramic substrate.

[0049] The titanium powder is coated on the surface of the TiO2 ceramic substrate using a brush, or the titanium powder is dispersed in a solvent to form a titanium powder dispersion liquid, and then coated on the surface of the TiO2 ceramic, and dried to obtain a TiO2 ceramic with titanium powder coated on the surface.

[0050] In an alternative embodiment, the amount of titanium powder applied to the surface of the titanium dioxide ceramic is 0.0008-0.002 g / cm 2 .

[0051] In an alternative embodiment, the solvent of the titanium powder dispersion liquid is ethanol or deionized water; and the concentration of the titanium powder dispersion liquid is 5-15 mol / L.

[0052] The titanium dioxide ceramic coated with titanium powder is heat treated under certain conditions to cause lattice distortion on the surface of the titanium dioxide ceramic; and the titanium powder layer on the surface of the titanium dioxide ceramic after the reaction is removed.

[0053] In an alternative embodiment, the heat treatment temperature is 500-1050°C, the heat treatment time is 0.5-8 h, the heating rate is 2-10°C / min, and the environmental atmosphere is vacuum or inert gas atmosphere; preferably, the heat treatment temperature is 800-900°C, the heat treatment time is 0.5-3 h, and the environmental atmosphere is vacuum or inert gas atmosphere.

[0054] In an alternative embodiment, after the heat treatment, the composition of the titanium powder layer after the reaction on the surface includes titanium powder and titanium oxide (such as Ti2O, Ti3O5, etc.).

[0055] A titanium dioxide nanorod crystal layer is grown in situ on the surface of the titanium dioxide ceramic with lattice distortion through a hydrothermal reaction. Specifically, a mixed solution is obtained by slowly adding 36-38% hydrochloric acid into deionized water while stirring, and then adding tetrabutyl titanate into the solution while stirring until the solution is clear; the titanium dioxide ceramic is subjected to purging or cleaning to remove the residual titanium powder on the surface after the heat treatment, and then the titanium dioxide ceramic with lattice distortion on the surface is placed into a hydrothermal reactor, the mixed solution is poured into the hydrothermal reactor, and finally the reaction is carried out at a temperature of 120-180°C for 4-20 h to obtain a titanium dioxide ceramic with a titanium dioxide nanorod crystal layer grown on the surface. Preferably, the temperature of the hydrothermal reaction is 140-160°C, and the hydrothermal reaction time is 5-10 h.

[0056] In an alternative embodiment, the volume ratio of hydrochloric acid to deionized water is 1-2:1-2. The volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water in the mixed solution is 1:10-30:10-30.

[0057] The following examples are further illustrated in detail to explain the present application. It should also be understood that the following examples are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present application are within the scope of protection of the present application. The specific process parameters in the following examples are only one example in the appropriate range, i.e. those skilled in the art can make appropriate selection within the range according to the description herein, and are not limited to the specific values in the following examples.

[0058] Example 1

[0059] The method for growing a layer of titania nanorod crystals in situ on the surface of titania ceramic provided in this embodiment 1 comprises the following steps:

[0060] (1) Take the titania ceramic obtained by dry pressing and sintering (sintering temperature is 1200℃, sintering time is 3h, and the heating rate is 3℃ / min) as the base material, disperse 0.1g of titanium powder into 20mL of anhydrous ethanol to obtain a titanium powder dispersion liquid, and use a brush to apply the obtained dispersion liquid on the surface of the titania ceramic. After drying the titania ceramic coated with the titanium powder dispersion liquid, heat it to 900℃ at a heating rate of 10℃ / min under vacuum atmosphere, keep it at this temperature for 2h, and then cool it down with the furnace to obtain the titania ceramic coated with titanium powder after heat treatment; remove the titanium powder layer after surface reaction to obtain the titania ceramic with lattice distortion on the surface;

[0061] (2) First, slowly add hydrochloric acid with a concentration of 36% to 38% into deionized water while stirring, then add tetrabutyl titanate while stirring, and stir until the solution is clear to obtain a mixed solution; wherein the volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water is 1:20:20;

[0062] (3) Put the titania ceramic with lattice distortion on the surface obtained in step (1) into a hydrothermal reaction kettle, then pour the mixed solution obtained in step (2) into the 200mL hydrothermal reaction kettle (the filling degree is controlled to be about 40%, and the hydrothermal reaction kettle is a sealed high-temperature and high-pressure hydrothermal reaction kettle with a polytetrafluoroethylene lining in the metal shell), heat the reaction kettle through an electric heating air drying oven, and react at a temperature of 150℃ for 6 hours; after the reaction is completed, cool the hydrothermal reaction kettle to room temperature, open it, take out the titania ceramic, and rinse it with anhydrous ethanol and deionized water for 2-3 times, and finally dry it at 100℃ to obtain the titania ceramic with a layer of titania nanorod crystals grown in situ on the surface.

[0063] Example 2

[0064] The method for growing a layer of titania nanorod crystals in situ on the surface of titania ceramic provided in this embodiment 2 comprises the following steps:

[0065] (1) The titanium dioxide ceramic obtained by dry pressing and sintering (sintering temperature: 1200°C, sintering time: 3h, and temperature increasing rate: 3°C / min) is used as the base material, 0.1g of titanium powder is dispersed in 20mL of anhydrous ethanol to obtain a titanium powder dispersion liquid, and the obtained dispersion liquid is applied on the surface of the titanium dioxide ceramic with a brush. The titanium dioxide ceramic coated with the titanium powder dispersion liquid is dried and then heated to 900°C at a temperature increasing rate of 10°C / min under vacuum atmosphere, and then cooled in the furnace after being kept at 900°C for 2h to obtain the titanium dioxide ceramic coated with titanium powder and heat-treated; the titanium powder layer on the surface after reaction is removed to obtain the titanium dioxide ceramic with lattice distortion on the surface;

[0066] (2) First, hydrochloric acid with a concentration of 36% to 38% is slowly added dropwise in deionized water while stirring, and then tetrabutyl titanate is added dropwise while stirring until the solution is clear to obtain a mixed solution; the volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water is 1:20:20;

[0067] (3) The titanium dioxide ceramic with lattice distortion on the surface obtained in step (1) is placed in a hydrothermal reaction kettle, and then the mixed solution obtained in step (2) is poured into the 200mL hydrothermal reaction kettle (the filling degree is controlled to be about 40%, and the hydrothermal reaction kettle is a sealed high-temperature and high-pressure hydrothermal reaction kettle with a polytetrafluoroethylene lining in the metal shell); the reaction kettle is heated by an electric heating air drying oven, and the reaction is carried out at a temperature of 150°C for 13h; after the reaction is completed, the hydrothermal reaction kettle is cooled to room temperature and opened, the titanium dioxide ceramic is taken out and washed with anhydrous ethanol and deionized water for 2 to 3 times, and finally dried at 100°C to obtain the titanium dioxide ceramic with a layer of titanium dioxide nanorod crystals grown in situ on the surface.

[0068] Example 3

[0069] The method for growing a layer of titanium dioxide nanorod crystals in situ on the surface of the titanium dioxide ceramic provided in this embodiment 3 comprises the following steps:

[0070] (1) The titanium dioxide ceramic obtained by dry pressing and sintering (sintering temperature: 1200°C, sintering time: 3h, and temperature increasing rate: 3°C / min) is used as the base material, 0.1g of titanium powder is dispersed in 20mL of deionized water to obtain a titanium powder dispersion liquid, and the obtained dispersion liquid is applied on the surface of the titanium dioxide ceramic with a brush. The titanium dioxide ceramic coated with the titanium powder dispersion liquid is dried and then heated to 900°C at a temperature increasing rate of 10°C / min under vacuum atmosphere, and then cooled in the furnace after being kept at 900°C for 1h to obtain the titanium dioxide ceramic coated with titanium powder and heat-treated; the titanium powder layer on the surface after reaction is removed to obtain the titanium dioxide ceramic with lattice distortion on the surface;

[0071] (2) first slowly add hydrochloric acid with a concentration of 36% to 38% in deionized water while stirring, then add tetrabutyl titanate while stirring, and stir until the solution is clear to obtain a mixed solution; wherein the volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water is 1:30:30;

[0072] (3) Put the titanium dioxide ceramic with lattice distortion on the surface obtained in step (1) into a hydrothermal reactor, then pour the mixed solution obtained in step (2) into a 200 mL hydrothermal reactor (the filling degree is controlled to be about 40%, and the hydrothermal reactor is a sealed high-temperature and high-pressure hydrothermal reactor with a polytetrafluoroethylene lining in a metal shell), heat the reactor in an electric heating air drying oven, and react at a temperature of 150°C for 10 hours; after the reaction is completed, cool the hydrothermal reactor to room temperature, open it, take out the titanium dioxide ceramic, and rinse it with anhydrous ethanol and deionized water for 2-3 times, and finally dry it at 100°C to obtain a titanium dioxide ceramic with a layer of titanium dioxide nanorod crystals grown in situ on the surface of the titanium dioxide ceramic.

[0073] Example 4

[0074] The method for growing a layer of titanium dioxide nanorod crystals in situ on the surface of a titanium dioxide ceramic provided in this embodiment 4 includes the following steps:

[0075] (1) Take the titanium dioxide ceramic obtained by freeze-drying and sintering (wherein the freeze-drying temperature is -80°C, and the time is 10h; the sintering temperature is 1200°C, the sintering time is 3h, and the heating rate is 2°C / min) as the base material, disperse 0.1g of titanium powder into 20mL of deionized water to obtain a titanium powder dispersion, and use a brush to apply the obtained dispersion on the surface of the titanium dioxide ceramic. After drying the titanium dioxide ceramic coated with the titanium powder dispersion, heat it to 900°C at a heating rate of 10°C / min in a vacuum atmosphere, keep it at this temperature for 1h, and then cool it with the furnace to obtain a titanium dioxide ceramic coated with titanium powder after heat treatment; remove the titanium powder layer after surface reaction to obtain a titanium dioxide ceramic with lattice distortion on the surface;

[0076] (2) first slowly add hydrochloric acid with a concentration of 36% to 38% in deionized water while stirring, then add tetrabutyl titanate while stirring, and stir until the solution is clear to obtain a mixed solution; wherein the volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water is 1:30:30;

[0077] (3) The titanium dioxide ceramic with lattice distortion on the surface obtained in step (1) is placed in a hydrothermal reactor, and then the mixed solution obtained in step (2) is poured into a 200 mL hydrothermal reactor (the filling degree is controlled to be about 40%, and the hydrothermal reactor is a sealed high-temperature and high-pressure hydrothermal reactor with a polytetrafluoroethylene lining in the metal shell), and the reactor is heated by an electric blower drying oven and reacted at a temperature of 150° C. for 8 hours; after the reaction is completed, the hydrothermal reactor is cooled to room temperature and opened, the titanium dioxide ceramic is taken out and rinsed with anhydrous ethanol and deionized water for 2 to 3 times, and finally dried at 100° C. to obtain a titanium dioxide ceramic with an in situ grown titanium dioxide nanorod crystal layer on the surface.

[0078] Figure 1 This SEM image shows the titanium powder layer remaining on the surface after heat treatment, and a titanium dioxide ceramic with lattice distortion on the surface. The image shows that the titanium powder coated on the titanium dioxide ceramic remains granular after the thermal reaction with the titanium dioxide ceramic. Microscopically, no titanium powder adheres to the surface due to the thermal reaction.

[0079] Figure 2 The following image shows a titanium powder layer after heat treatment and a titanium dioxide ceramic with lattice distortion on its surface. As can be seen from the image, the titanium powder reacts with the titanium dioxide ceramic surface to form a titanium powder layer, which can easily detach from the titanium dioxide ceramic surface after heat treatment.

[0080] Figure 3 The following are XRD results for the titanium powder raw material and the titanium powder layer removed from the surface after heat treatment of the titanium dioxide ceramic. As can be seen, the titanium powder raw material exhibits XRD diffraction peaks solely characteristic of titanium metal, but the removed titanium powder layer exhibits XRD diffraction peaks characteristic of titanium metal as well as those of various titanium oxides. This indicates that during the thermal reaction between the titanium powder and the titanium dioxide ceramic surface, the titanium dioxide absorbs oxygen from the titanium dioxide, generating various titanium oxides.

[0081] Figure 4 (a) and (b) are SEM images of the titanium powder raw material; (c) and (d) are SEM images of the titanium powder layer removed from the surface of the titanium dioxide ceramic after heat treatment (magnifications of ×100, ×2000, ×100, and ×2000, respectively). As can be seen, the titanium powder surface before the thermal reaction is noticeably smooth, while the titanium powder layer after the thermal reaction exhibits an expanded surface morphology. This indicates that during the thermal reaction with the titanium dioxide ceramic surface, the titanium powder absorbs oxygen from the titanium dioxide, generating various titanium oxides. The density of titanium oxides is greater than that of titanium metal, resulting in their volume expansion.

[0082] Figure 5XRD results of the titanium dioxide ceramic substrate and the titanium dioxide ceramic substrate with lattice distortion on the surface after thermal reaction. As can be seen from the figure, before thermal reaction, the titanium dioxide ceramic substrate presents obvious diffraction peaks of rutile titanium dioxide. After thermal reaction, in addition to the diffraction peaks of rutile titanium dioxide, there are diffraction peaks of various titanium oxides, indicating that the titanium dioxide ceramic and titanium powder are thermally reacted, part of the oxygen in the titanium dioxide lattice on the surface is taken away by the titanium powder, and part of the lattice is distorted to form titanium oxide.

[0083] Figure 6 SEM pictures of the titanium dioxide ceramic as the substrate in Example 1 (a), and the titanium dioxide ceramic after in-situ growth of the titanium dioxide nanorod crystal layer on the surface for 6h (b). Figure 7 SEM pictures of the titanium dioxide ceramic after in-situ growth of the titanium dioxide nanorod crystal layer on the surface for 13h in Example 2. As can be seen from the figure, TiO2 nanorods are grown on the surface of the titanium dioxide ceramic substrate, and the size of the TiO2 nanorods also increases with the increase of the hydrothermal time.

[0084] Figure 8 SEM pictures of the titanium dioxide ceramic (a), the titanium dioxide ceramic with lattice distortion on the surface (b), and the titanium dioxide ceramic after in-situ growth of the titanium dioxide nanorod crystal layer on the surface (c) in Example 2. As can be seen from the figure, the titanium dioxide ceramic coated with titanium powder on the surface has obvious changes in morphology after thermal treatment. The titanium dioxide ceramic surface is reduced in the process of thermal etching by titanium powder, the TiO2 lattice on the surface of the ceramic is oxygen-deficient, and active growth sites of TiO2 nanorods are obtained. Then, after hydrothermal reaction under suitable conditions, TiO2 nanorods are grown on the lattice distortion sites on the surface of the ceramic.

[0085] Figure 9 SEM pictures of the titanium dioxide ceramic (a), the titanium dioxide ceramic with lattice distortion on the surface (b), and the titanium dioxide ceramic after in-situ growth of the titanium dioxide nanorod crystal layer on the surface (c) in Example 3. As can be seen from the figure, in this Example 3, TiO2 nanorods are in-situ grown on the surface of the titanium dioxide ceramic. In addition, compared with Example 1, due to the decrease of the hydrothermal time, the size of the TiO2 nanorods is obviously reduced.

[0086] Figure 10SEM images of the titanium dioxide ceramic (a), the titanium dioxide ceramic with lattice distortion on the surface (b) and the titanium dioxide ceramic after growing a layer of titanium dioxide nanorod crystals on the surface (c) in Example 4. As can be seen from the images, in this Example 4, a layer of TiO2 nanorod crystals was grown in situ on the surface of the titanium dioxide ceramic. In addition, compared with Examples 1-3, the ceramic substrate prepared by different methods can also grow TiO2 nanorods on the surface, only the size and morphology of the TiO2 nanorods are different.

[0087] Figure 11 SEM images of the titanium dioxide ceramic (a), the titanium dioxide ceramic with lattice distortion on the surface (b) and the titanium dioxide ceramic after growing a layer of titanium dioxide nanorod crystals on the surface (c) in Example 4. As can be seen from the images, in this Example 4, a layer of TiO2 nanorod crystals was grown in situ on the surface of the titanium dioxide ceramic. In addition, compared with Examples 1-3, the ceramic substrate prepared by different methods can also grow TiO2 nanorods on the surface, only the size and morphology of the TiO2 nanorods are different.

[0088] Comparative Example 1

[0089] The method for growing TiO2 nanorods by TiO2 seeds coated on the surface of the ceramic substrate in this Comparative Example 1 includes the following steps:

[0090] (1) The titanium dioxide ceramic obtained by dry pressing and sintering (sintering temperature of 1200°C, sintering time of 3h, and heating rate of 3°C / min) was used as the substrate material. The substrate material was immersed in tetrabutyl titanate for 10s and then heat treated at 600°C in a muffle furnace for 3h to obtain a titanium dioxide ceramic coated with TiO2 seeds on the surface;

[0091] (2) First, hydrochloric acid with a concentration of 36%-38% was slowly added to deionized water while stirring, and then tetrabutyl titanate was added while stirring until the solution was clear to obtain a mixed solution. The volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water was 1:20:20;

[0092] (3) The titanium dioxide ceramic coated with TiO2 seeds obtained in step (1) was placed in a hydrothermal reactor, and then the mixed solution obtained in step (2) was poured into the 200mL hydrothermal reactor (the filling degree was controlled to be about 40%, and the hydrothermal reactor was a sealed high-temperature and high-pressure hydrothermal reactor with a polytetrafluoroethylene lining in the metal shell). The reactor was heated by an electric heating air drying oven, and the reaction was carried out at a temperature of 150°C for 13 hours. After the reaction was completed, the hydrothermal reactor was cooled to room temperature and opened, the titanium dioxide ceramic was taken out and rinsed with anhydrous ethanol and deionized water for 2-3 times, and finally dried at 100°C to obtain a titanium dioxide ceramic with a layer of titanium dioxide nanorod crystals grown on the surface of the titanium dioxide ceramic by TiO2 seeds.

[0093] Comparative Example 2

[0094] Comparative Example 2 provides a method for growing a layer of titania nanorod crystals in situ on the surface of a titania ceramic substrate under the condition that the heat treatment temperature is too low, comprising the following steps:

[0095] (1) Using a titania ceramic obtained by dry pressing and sintering (sintering temperature of 1200°C, sintering time of 3h, and heating rate of 3°C / min) as a base material, 0.1g of titanium powder was dispersed in 20mL of anhydrous ethanol to obtain a titanium powder dispersion liquid, and the obtained dispersion liquid was applied to the surface of the titania ceramic using a brush. The titania ceramic coated with the titanium powder dispersion liquid was dried and then heated to 400°C at a heating rate of 10°C / min under vacuum, and after being kept at this temperature for 2h, it was cooled in the furnace to obtain a titania ceramic after heat treatment and coating with titanium powder on the surface; the layer of titanium powder after surface reaction was removed to obtain a titania ceramic after heat treatment;

[0096] (2) First, hydrochloric acid with a concentration of 36% to 38% was slowly added to deionized water while stirring, and then tetrabutyl titanate was added while stirring until the solution was clear to obtain a mixed solution; the volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water was 1:20:20;

[0097] (3) The titania ceramic after heat treatment obtained in step (1) was placed in a hydrothermal reaction kettle, and then the mixed solution obtained in step (2) was poured into a 200mL hydrothermal reaction kettle (the filling degree was controlled to be about 40%, and the hydrothermal reaction kettle was a sealed high-temperature and high-pressure hydrothermal reaction kettle with a polytetrafluoroethylene lining in a metal shell); the reaction kettle was heated by an electric heating air drying oven, and the reaction was carried out at a temperature of 150°C for 13 hours; after the reaction was completed, the hydrothermal reaction kettle was cooled to room temperature and opened, the titania ceramic was taken out and washed with anhydrous ethanol and deionized water for 2-3 times, and finally it was dried at 100°C to obtain a titania ceramic without a layer of titania nanorod crystals on the surface.

[0098] Comparative Example 3

[0099] Comparative Example 3 provides a method for growing a layer of titania nanorod crystals in situ on the surface of a titania ceramic substrate under the condition that the heat treatment temperature is too high, comprising the following steps:

[0100] (1) taking the titanium dioxide ceramic obtained by dry pressing and sintering (sintering temperature: 1200°C, sintering time: 3h, and temperature increasing rate: 3°C / min) as the base material, dispersing 0.1g of titanium powder into 20mL of anhydrous ethanol to obtain a titanium powder dispersion liquid, and smearing the obtained dispersion liquid on the surface of the titanium dioxide ceramic with a brush. After drying the titanium dioxide ceramic smeared with the titanium powder dispersion liquid, the titanium dioxide ceramic is heated to 1200°C at a temperature increasing rate of 10°C / min under vacuum atmosphere, and then cooled down after being kept at 1200°C for 2h to obtain the titanium dioxide ceramic coated with titanium powder and heat-treated; and removing the titanium powder layer after surface reaction to obtain the titanium dioxide ceramic with lattice distortion on the surface;

[0101] (2) slowly adding hydrochloric acid with a concentration of 36% to 38% into deionized water while stirring, and then adding tetrabutyl titanate while stirring, until the solution is clear to obtain a mixed solution; wherein the volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water is 1:20:20;

[0102] (3) putting the titanium dioxide ceramic with lattice distortion on the surface obtained in step (1) into a hydrothermal reaction kettle, and then pouring the mixed solution obtained in step (2) into the 200mL hydrothermal reaction kettle (the filling degree is controlled to be about 40%, and the hydrothermal reaction kettle is a sealed high-temperature and high-pressure hydrothermal reaction kettle with a polytetrafluoroethylene lining in the metal shell), and heating the reaction kettle through an electric heating air drying oven, and reacting at a temperature of 150°C for 13h; after the reaction is completed, the hydrothermal reaction kettle is cooled to room temperature and opened, the titanium dioxide ceramic is taken out and washed with anhydrous ethanol and deionized water for 2 to 3 times, and finally dried at 100°C to obtain the titanium dioxide ceramic without the titanium dioxide nanorod crystal layer on the surface.

[0103] Comparative Example 4

[0104] The comparative example 4 provides a method for growing a titanium dioxide nanorod crystal layer on the surface of a titanium dioxide ceramic base in situ under the condition that the hydrothermal reaction temperature is too low, which comprises the following steps:

[0105] (1) taking the titanium dioxide ceramic obtained by dry pressing and sintering (sintering temperature: 1200°C, sintering time: 3h, and temperature increasing rate: 3°C / min) as the base material, dispersing 0.1g of titanium powder into 20mL of anhydrous ethanol to obtain a titanium powder dispersion liquid, and smearing the obtained dispersion liquid on the surface of the titanium dioxide ceramic with a brush. After drying the titanium dioxide ceramic smeared with the titanium powder dispersion liquid, the titanium dioxide ceramic is heated to 1200°C at a temperature increasing rate of 10°C / min under vacuum atmosphere, and then cooled down after being kept at 1200°C for 2h to obtain the titanium dioxide ceramic coated with titanium powder and heat-treated; and removing the titanium powder layer after surface reaction to obtain the titanium dioxide ceramic with lattice distortion on the surface;

[0106] (2) first slowly add hydrochloric acid with a concentration of 36% to 38% in deionized water while stirring, then add tetrabutyl titanate while stirring, and stir until the solution is clear to obtain a mixed solution; wherein the volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water is 1:20:20;

[0107] (3) Put the titanium dioxide ceramic with lattice distortion on the surface obtained in step (1) into a hydrothermal reactor, then pour the mixed solution obtained in step (2) into a 200 mL hydrothermal reactor (the filling degree is controlled to be about 40%, and the hydrothermal reactor is a sealed high-temperature and high-pressure hydrothermal reactor with a polytetrafluoroethylene lining in a metal shell), heat the reactor in an electric heating air drying oven, and react at a temperature of 100°C for 13 hours; after the reaction is completed, cool the hydrothermal reactor to room temperature and open it, take out the titanium dioxide ceramic and rinse it with anhydrous ethanol and deionized water for 2-3 times, and finally dry it at 100°C to obtain a titanium dioxide ceramic without a titanium dioxide nanorod crystal layer on the surface.

[0108] Comparative Example 5

[0109] In this comparative example 5, a method for growing a titanium dioxide nanorod crystal layer on the surface of a titanium dioxide ceramic substrate in situ under the condition of too long hydrothermal reaction time is provided, which comprises the following steps:

[0110] (1) Take the titanium dioxide ceramic obtained by dry pressing and sintering (sintering temperature is 1200°C, sintering time is 3h, and heating rate is 3°C / min) as the substrate material, disperse 0.1g of titanium powder into 20mL of anhydrous ethanol to obtain a titanium powder dispersion liquid, and use a brush to apply the obtained dispersion liquid on the surface of the titanium dioxide ceramic. After drying the titanium dioxide ceramic coated with the titanium powder dispersion liquid, heat it to 900°C at a heating rate of 10°C / min in a vacuum atmosphere, keep it at this temperature for 2h, and then cool it in the furnace to obtain a titanium dioxide ceramic coated with titanium powder and heat treated; remove the titanium powder layer after surface reaction to obtain a titanium dioxide ceramic with lattice distortion on the surface;

[0111] (2) first slowly add hydrochloric acid with a concentration of 36% to 38% in deionized water while stirring, then add tetrabutyl titanate while stirring, and stir until the solution is clear to obtain a mixed solution; wherein the volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water is 1:20:20;

[0112] (3) Put the titanium dioxide ceramic with lattice distortion on the surface obtained in step (1) into a hydrothermal reactor, and then pour the mixed solution obtained in step (2) into the 200 mL hydrothermal reactor (the filling degree is controlled to be about 40%, and the hydrothermal reactor is a sealed high-temperature and high-pressure hydrothermal reactor with a polytetrafluoroethylene lining in a metal shell), heat the reactor through an electric heating air drying oven, and react at 150°C for 19 hours; after the reaction is completed, cool the hydrothermal reactor to room temperature, open it, take out the titanium dioxide ceramic, and rinse it with anhydrous ethanol and deionized water for 2-3 times, and finally dry it at 100°C to obtain the titanium dioxide ceramic with a layer of titanium dioxide nanorod crystals grown in situ on the surface.

[0113] Figure 12 The SEM picture of the titanium dioxide nanorod crystal layer grown by using the seed coating method in Comparative Example 1. As can be seen from the figure, since the TiO2 seed is in the form of particles, the titanium dioxide nanorods grown on the surface of the ceramic substrate also present a nanoflower shape, and cannot be grown in situ on the surface of the titanium dioxide ceramic.

[0114] Figure 13 The SEM picture of the titanium dioxide ceramic after the hydrothermal reaction in Comparative Example 2. As can be seen from the figure, the heat treatment temperature is too low, the degree of oxygen deficiency of the TiO2 lattice on the surface of the titanium dioxide ceramic substrate is insufficient, the lattice distortion cannot occur, the active growth sites are difficult to obtain, the titanium dioxide nanorods cannot be grown in situ, and the morphology of the titanium dioxide ceramic surface after the reaction with titanium powder is still maintained.

[0115] Figure 14 The SEM picture of the titanium dioxide ceramic after the hydrothermal reaction in Comparative Example 3. As can be seen from the figure, the heat treatment temperature is too high, the degree of TiO2 lattice distortion on the surface of the titanium dioxide ceramic substrate is too high. Although there are active growth sites, the lattice difference is too large, the titanium dioxide nanorods cannot be grown in situ, and the morphology of the titanium dioxide ceramic surface after the reaction with titanium powder is still maintained.

[0116] Figure 15 The SEM picture of the titanium dioxide ceramic after the hydrothermal reaction in Comparative Example 4. As can be seen from the figure, the hydrothermal reaction temperature is too low, the chemical driving force for the growth of the titanium dioxide nanorods at the active sites is insufficient, the titanium dioxide nanorods cannot be grown in situ, and the morphology of the titanium dioxide ceramic surface after the reaction with titanium powder is still maintained.

[0117] Figure 16 The SEM picture of the titanium dioxide ceramic after the hydrothermal reaction in Comparative Example 5. As can be seen from the figure, the hydrothermal reaction time is too long, the titanium dioxide nanorods on the surface of the titanium dioxide ceramic are filled too much, and are too dense, so that the nanorod crystals grown in situ on the titanium dioxide ceramic lose the morphology characteristics of the nanorods as a whole.

Claims

1. A method for in-situ growth of a titanium dioxide nanorod crystal layer on a titanium dioxide ceramic surface, characterized in that: Includes: Includes the following steps: (1) applying titanium powder to the surface of titanium dioxide ceramics, or dispersing titanium powder in a solvent to form a titanium powder dispersion, and then applying it to the surface of titanium dioxide ceramics, and after drying, obtaining titanium dioxide ceramics with titanium powder coated on the surface; (2) heat-treating a titanium dioxide ceramic coated with titanium powder under certain conditions to cause lattice distortion on the surface of the titanium dioxide ceramic; and removing the titanium powder layer after the reaction on the surface of the titanium dioxide ceramic; the heat treatment parameters include: a heat treatment temperature of 500 to 1050° C. and a holding time of 0.5 to 8 hours; (3) In situ growth of a titanium dioxide nanorod crystal layer on the surface of the titanium dioxide ceramic with lattice distortion occurs by a hydrothermal reaction; the temperature of the hydrothermal reaction is 120 to 180° C., and the time is 4 to 20 hours.

2. The method according to claim 1, characterized in that In step (1), the amount of titanium powder applied to the surface of the titanium dioxide ceramic is 0.0008 to 0.02 g / cm 2 .

3. The method according to claim 1, characterized in that In step (1), the solvent of the titanium powder dispersion is ethanol or deionized water; the concentration of the titanium powder dispersion is 5 to 15 mol / L.

4. The method according to claim 1, wherein In step (2), the heat treatment temperature is 800-900° C., and the holding time is 0.5-3 h.

5. The method according to claim 4, characterized in that In step (2), the heat treatment atmosphere is a vacuum or inert gas atmosphere.

6. The method according to claim 1, characterized in that In step (2), after heat treatment, the composition of the titanium powder layer after surface reaction includes: titanium powder and titanium oxide.

7. The method according to claim 1, characterized in that In step (3), the hydrothermal reaction comprises: first preparing a mixed solution of tetrabutyl titanate, hydrochloric acid and deionized water, then placing the titanium dioxide ceramic with lattice distortion on the surface into the mixed solution and performing a hydrothermal reaction in a hydrothermal reactor to obtain a titanium dioxide nanorod crystal layer grown in situ on the surface of the titanium dioxide ceramic.

8. The method according to claim 7, characterized in that The volume ratio of tetrabutyl titanate, hydrochloric acid and deionized water in the mixed solution is 1:10-30:10-30; The concentration of the hydrochloric acid is 36-38%.

9. The method according to claim 1, characterized in that In step (2), the titanium powder layer after the reaction on the surface of the titanium dioxide ceramic is removed by blowing or washing.

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