Preparation method of small-size single-phase titanium black

Abstract

The invention belongs to the field of inorganic materials, discloses a preparation method of small-size and single-phase titanium black, and solves the problems that the preparation of titanium black through carbon thermal reduction needs a relatively high temperature, the particle size of a product is large, and a crystal phase is difficult to regulate and control. The small-size single-phase titanium black is prepared by taking a titanic acid nanotube with high specific surface area, rich hydroxyl groups on the surface and high reaction activity or titanium dioxide derived from the titanic acid nanotube as a titanium source and a carbon source with good water solubility and active groups through hydrothermal and calcining treatment. Carbon is more easily and uniformly distributed in a titanium source by regulating and controlling a hydrothermal medium and improving the surface property of a carbon thermal reduction precursor and the contact mode of the Ti source and a carbon source, an unsaturated bond is introduced, additional reduction electrons are provided for a system, and in addition, due to the unique hollow tubular structure, the carbon-carbon composite material has a good application prospect. According to the preparation method, a reducing gas generated in the carbon thermal reduction process can permeate into the material, the reduction efficiency is improved, and the possibility of non-uniform reduction is reduced, so that the small-size and single-phase titanium black is obtained at a relatively low temperature.

Description

Technical Field

[0001] The present invention belongs to the field of inorganic materials, and particularly relates to a preparation method of titanium suboxide. Background Art

[0002] Titanium suboxide Ti n O 2n-1 (3≤n≤10) is a class of blue-black non-stoichiometric titanium oxides. Every n layers of TiO 6 octahedra will have a layer of oxygen defects, and this layer of oxygen defects can endow titanium suboxide with excellent physical and chemical properties, such as a large electrochemical window, high conductivity, catalytic activity, visible light responsiveness, and it can also balance excellent chemical and electrochemical stabilities, and acid / alkali corrosion resistance. Therefore, titanium suboxide can be widely applied in new energy, electrocatalysis, photocatalysis and even biomedicine and other fields. However, impure phase and large particle size greatly limit its application performance. Due to the strong binding energy between small-sized grains, small-sized titanium suboxide is more conducive to sintering a dense and better-conductive electrode; in the field of photocatalysis, small-sized catalysts also have higher photocatalytic efficiency; in the field of gas sensors, small size can provide high charge transfer efficiency for the substrate, converting the kinetic energy of more mobile charges into heat energy, thereby improving the sensitivity of the sensor; especially in the field of drug carriers, small size can effectively embed and adsorb drug molecules, making the chemotherapy drugs form a higher local concentration in the carrier and reducing the number of drug administrations.

[0003] At present, the preparation methods of titanium suboxide include gas-phase reduction, metal reduction, and carbothermal reduction, etc. The gas-phase reduction method lacks steric hindrance and generates H 2O will exacerbate the melting and sintering of the product and is not conducive to the preparation of small-sized titanium suboxide. Metal / hydride reduction requires subsequent impurity removal, increasing the process flow and having low economic benefits. The carbothermal reduction process is simple and has low raw material costs. However, through thermodynamic analysis, it can be seen that there are problems in the preparation of titanium suboxide by carbothermal reduction, such as the theoretical reduction temperatures of different types of titanium suboxide being relatively close and the reduction temperature being relatively high. Therefore, it is difficult to achieve the preparation of small-sized and single-phase titanium suboxide. To achieve the preparation of small-sized single-phase titanium suboxide, the following directions can be explored: (1) Select a suitable titanium / carbon combination. If there is a certain group in the selected titanium source and carbon source, the carbon source can be fully dispersed in the titanium source; (2) After pretreatment, obtain a precursor with excellent surface properties and the contact mode between Ti and C. For example, Magnéli phase titanium suboxide can be prepared at a lower reduction temperature by methods such as high-pressure granulation, sol-gel, or constructing a Mxene layered structure; (3) Improve the calcination conditions. For example, microwave radiation heating can be used, so that the precursor can rise / cool to the specified temperature in a short time, preventing the product from being re-oxidized. All in all, the key to preparing small-sized and single-phase titanium suboxide lies in improving the composite mode and composite effect of Ti and C through physical or chemical means.

[0004] Xinjun Bao et al. (Micro&Nano Letters, 2020, 15, 984 - 987) provided a method for preparing titanium suboxide by pressure granulation carbothermal reduction. The steps include: mixing TiO 2 with polyvinyl alcohol powder in an equal mass ratio, and then granulating the obtained mixed powder by uniaxial hydraulic pressing. Finally, heat treatment is carried out under a nitrogen atmosphere to obtain titanium suboxide. The average particle size of the titanium suboxide obtained by this method is 200 - 500 nm. Although this method can inhibit the sintering growth of particles through the pressing effect, the composite effect of C and Ti has not been improved, so it is difficult to prepare single-phase titanium suboxide. Xinyong Tao et al. (Nano Letter. 2014, 14, 5288 - 5294) obtained single-phase Ti 2 O by hydrogen reduction of TiO 4 O 7 at 1050 °C, and the particle size is 80 - 400 nm. This method can accurately control the phase regulation of titanium suboxide by hydrogen reduction, but it is difficult to achieve large-scale production. David Portehault et al. (ACS Nano, 2011, 5, 9052 - 9061) provided a sol-gel method for preparing titanium suboxide. The process is as follows: Using tetraethyl titanate as the titanium source, reacting with poly(ethyleneimine) in an ethanol solvent to form a transparent gel, and then calcining under a nitrogen atmosphere, single-phase Ti 4 O 7。Its average particle size is about 100 nm. This method uses the sol-gel method to improve the effective contact between Ti and C, thereby achieving the preparation of small-sized and single-phase titanium suboxide. However, the sol-gel method has a complex process, and since a gel structure needs to be constructed, more carbon sources are required for support, resulting in a relatively high cost. Tomohiro Takeuchi et al. (Catalysts, 2017, 7, 65) used microwave radiation heating to achieve small-sized single-phase preparation. The specific process is to first obtain a mixed powder of TiO 2 and polyvinylpyrrolidone, and then heat it in a microwave radiation device. Pure-phase Ti 4 O 7 can be obtained by reacting at 950 °C for 30 min, and the particle size is similar to that of the initial TiO 2 , only about 60 nm. Using the microwave radiation heating method, the reaction temperature can be quickly reached, and since the precursor can absorb microwave energy, better reaction activity can be obtained, thus achieving small-sized and single-phase preparation. However, due to the uneven absorption rate of the material in the microwave radiation heating method, local overheating and particle agglomeration are likely to occur, which affects the final product structure and distribution uniformity, has poor repeatability, and reduces the yield and product quality.

[0005] The above preparation methods can all solve the preparation problems of small-sized and single-phase titanium suboxide to a certain extent, but they all have disadvantages. Summary of the Invention

[0006] In view of the problem that it is difficult to achieve single-phase and small-sized preparation in the existing carbothermal reduction for preparing titanium suboxide, the present invention proposes a method for preparing small-sized and single-phase titanium suboxide. By selecting a combination of a titanium source with a high specific surface area and a carbon source with high reduction activity, and then by regulating the hydrothermal conditions, the contact mode and surface properties of Ti and C are improved, and finally small-sized and single-phase titanium suboxide particles are prepared at a relatively low calcination temperature (850 °C).

[0007] To achieve the above object, the technical solution of the present invention is realized as follows:

[0008] A method for preparing small-sized and single-phase titanium suboxide, the steps are as follows:

[0009] (1) Disperse the titanium source and the carbon source in distilled water, and obtain a precursor powder through a hydrothermal reaction; wherein, the titanium source is titanium nanotubes (NTA) or titanium dioxide derived from titanium nanotubes (TiO 2 ) derived from NTA;

[0010] (2) The precursor powder is calcined to obtain small-sized and single-phase titanium suboxide.

[0011] Select NTA or TiO 2as the titanium source. Compared with commercially available TiO 2 , the hollow tubular-structured NTA has higher reactivity and a larger specific surface area (350 - 420 m 2 / g). Moreover, the tubular structure can inhibit the melting and sintering of the product during high-temperature calcination, which is beneficial for the preparation of small-sized titanium suboxide; while the TiO 2 derived from NTA can retain high reactivity, a large specific surface area, and some tubular structures, and has better particle dispersibility and particle size distribution. Using a carbon source as a reducing agent, after hydrothermal reaction, the reducing agent can form a carbon layer on the surface of NTA. During the subsequent calcination process, in addition to acting as a reducing agent, it can also act as a growth inhibitor and a pore-forming agent. By regulating the ratio of Ti to C and the amount of the hydrothermal medium (distilled water), a precursor with excellent surface properties (i.e., the surface contains more unsaturated bonds) and a suitable contact mode between Ti and C (i.e., the surface of the reduction product is still coated with a uniform carbon layer) is obtained, which will enable the calcination reduction in a tube furnace to be carried out at a lower temperature (850 °C). Meanwhile, by utilizing the steric hindrance effect of the carbon source, the preparation of small-sized, single-phase titanium suboxide is achieved.

[0012] The above-mentioned TiO 2 (which is anatase TiO 2 ) is formed by calcining and dehydrating the NTA prepared by the present invention. Its specific surface area is 70 - 85 m 2 / g, and the absolute value of the Zeta potential is 20 - 25 mV. Among them, the temperature of the calcination and dehydration treatment is 500 - 700 °C, and the time is 1 - 5 h.

[0013] In the above step (1), the mass ratio of the titanium source, the carbon source, and distilled water is 1:(0.2 - 1):(2.5 - 10).

[0014] In the above step (1), the carbon source is at least one of polyvinyl alcohol (PVA), polyethylene glycol (PEG 6000), polyvinylamide, glucose, sucrose, and citric acid.

[0015] In the above step (1), the temperature of the hydrothermal reaction is 180 - 250 °C, and the time is 8 - 24 h.

[0016] In the above step (2), the calcination treatment is carried out in an inert atmosphere, a reducing atmosphere, or a combined atmosphere of both. The gas flow rate is controlled at 50 - 200 mL / min.

[0017] In the above step (2), the temperature of the calcination treatment is 850 - 1050 °C, and the time is 2 - 5 h.

[0018] Small-sized, single-phase titanium suboxide prepared by the above preparation method.

[0019] The reaction mechanism of the present invention is as follows: The known reaction sequence of carbothermal reduction is: TiO 2 →Ti 10 O 19 →Ti 9 O 17 →···→Ti 4 O 7 →Ti 3 O 5 。 Through thermodynamic analysis, it can be known that the theoretical reduction temperatures between titanium suboxides with 4 ≤ n ≤ 10 are very close (about 50 °C), while the theoretical reduction temperatures of Ti 4 O 7 and Ti 3 O 5 differ greatly. However, the theoretical reduction temperatures of different types of titanium suboxides are affected by the reaction activity of the precursor to different degrees. Therefore, it is possible to achieve phase state regulation while preparing small-sized particles at a lower reduction temperature by improving the reaction activity. The key factors affecting the reaction activity of the preparation of single-phase and small-sized titanium suboxides by carbothermal reduction are the effective contact between Ti / C and the surface properties of the precursor. The present invention selects NTA or NTA-derived TiO 2 as the titanium source. Utilizing the high reaction activity of the titanium source, under hydrothermal action, an interfacial reaction occurs with the carbon source, enabling the carbon source to be fully adsorbed and spread on the surface of the titanium source, and polymerize and crosslink on its surface to form a network structure, improving the effective contact between Ti / C in the precursor; on the other hand, the unsaturated bonds formed after the carbon source is hydrothermally treated can provide additional reduction electrons for the reaction system, improving the reaction activity of the precursor, thereby realizing the preparation of single-phase titanium suboxide. In addition, the network structure formed by the carbon source on the surface of the Ti atom can play a steric hindrance effect and can effectively inhibit melting and sintering, which is beneficial to the preparation of small-sized titanium suboxide.

[0020] The beneficial effects produced by the present invention are:

[0021] (1) The present invention uses NTA as the precursor. Compared with the existing titanium precursors, NTA has rich surface hydroxyl groups, high exchange activity, high specific surface area, high reaction activity, and the tubular structure of NTA can inhibit the melting and sintering of the product during high-temperature calcination, which is beneficial to the preparation of small-sized titanium suboxide.

[0022] (2) The present invention uses NTA-derived TiO 2 as the precursor. Compared with NTA, the specific surface area and reaction activity have decreased to a certain extent, but compared with the existing commercial TiO 2 , it still has a higher specific surface area. In addition, it has better dispersibility, and the dissolution and precipitation rates remain relatively consistent (such as Figure 3The larger the absolute value of the Zeta potential shown, the better the dispersibility), which can make the generated precursor particles smaller and more uniformly distributed.

[0023] (3) Compared with the commonly used carbothermal reduction method, the preparation method provided by the present invention adopts a combination of a high specific surface area titanium source with a one-dimensional tubular structure and a highly reducing carbon source, and with the assistance of hydrothermal treatment, it improves the effective contact between Ti and C and introduces more reduction electrons into the system, thus enhancing the overall reaction activity. Furthermore, relying on the structural characteristics of the one-dimensional titanium source and the spatial polymerization inhibition effect of the carbon layer, suboxide titanium powder with controllable phase state and particle size can be obtained at a relatively low temperature (850 °C).

[0024] (4) Compared with the preparation methods using other types of reducing agents (H 2 , metals, etc.), the preparation method provided by the present invention requires lower costs, fewer parameters affecting the experiment, easier reaction control, and better safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is the SEM image of NTA (a) and NTA-derived TiO 2 (b) used in Example 11 of the present invention.

[0027] Figure 2 It is the FTIR spectrum of NTA used in the present invention.

[0028] Figure 3 It is the Zeta potential diagram of NTA-derived TiO 2 prepared in Example 11 of the present invention and the commercially available titanium dioxide of the comparative example.

[0029] Figure 4 It is the SEM image of the precursor powder prepared in Example 11 of the present invention.

[0030] Figure 5 It is the FTIR spectrum of the precursor powder prepared in Example 11 of the present invention.

[0031] Figure 6 It is the XRD spectrum of the product prepared in Example 11 of the present invention.

[0032] Figure 7SEM images of titanium suboxide powders prepared in Example 11(a) and Comparative Example (b) of the present invention. Detailed implementation mode

[0033] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0034] Example 1

[0035] The preparation method of small-sized, single-phase titanium suboxide in this example is as follows:

[0036] (1) a. Dissolve 120 g of titanium dioxide in 2 L of 11 M NaOH solution, stir to form a homogeneous colloid, and react at 110 °C for 36 h. Filter press to obtain a precipitate; b. Wash the above precipitate with water until the solution pH = 12 ± 0.3; c. Add an acidic solution with a pH of 0.8 to the solution in step b, and adjust the pH value of the solution to the pH value of the acidic solution used, aiming to displace the Na + , to form titanic acid, filter by suction, and then wash with water until pH ≥ 5 to obtain NTA, with a specific surface area of 350 m 2 / g.

[0037] (2) Control the mass ratio of NTA, polyacrylamide and distilled water to be 5:3:30, that is, disperse NTA (10 g) and polyacrylamide (6 g) in distilled water (60 g), and shear with a shear machine at a rate of 10000 r / min to obtain a precursor solution. Then pour the above precursor solution into a polytetrafluoroethylene high-pressure reaction kettle, and place the reaction kettle in an oven at a temperature of 250 °C for 8 h. After the reaction is completed, dry in a blast dryer at 80 °C to obtain precursor powder.

[0038] (3) Place the precursor powder in a tubular furnace, introduce argon into the tubular furnace at a gas flow rate of 150 mL / min, and heat it to 1050 °C at a rate of 10 °C / min and hold for 4 h to obtain small-sized, single-phase titanium suboxide.

[0039] Example 2

[0040] The preparation method of small-sized, single-phase titanium suboxide in this example is as follows:

[0041] (1) The specific preparation method of NTA is the same as that in step (1) of Example 1.

[0042] (2) Control the mass ratio of NTA, PEG 6000 to distilled water to be 5:3:30, that is, disperse NTA (10 g) and PEG 6000 (6 g) in distilled water (60 g), and shear with a shear machine at a rate of 10000 r / min to obtain a precursor solution. Then pour the above precursor solution into a polytetrafluoroethylene high-pressure reaction kettle, and place the reaction kettle in an oven at a temperature of 220 °C for 15 h. After the reaction is completed, dry it in a blast dryer at 80 °C to obtain a precursor powder.

[0043] (3) Place the precursor powder in a tube furnace, introduce argon into the tube furnace at a gas flow rate of 150 mL / min, and heat it to 980 °C at a rate of 10 °C / min and hold for 3 h to obtain small-sized, single-phase titanium suboxide.

[0044] Example 3

[0045] The preparation method of the small-sized, single-phase titanium suboxide in this example is as follows:

[0046] (1) The specific preparation method of NTA is the same as step (1) in Example 1.

[0047] (2) Control the mass ratio of NTA, PVA to distilled water to be 5:3:30, that is, disperse NTA (10 g) and PVA (6 g) in distilled water (60 g), and shear with a shear machine at a rate of 10000 r / min to obtain a precursor solution. Then pour the above precursor solution into a polytetrafluoroethylene high-pressure reaction kettle, and place the reaction kettle in an oven at a temperature of 200 °C for 20 h. After the reaction is completed, dry it in a blast dryer at 80 °C to obtain a precursor powder.

[0048] (3) Place the precursor powder in a tube furnace, introduce argon into the tube furnace at a gas flow rate of 150 mL / min, and heat it to 850 °C at a rate of 10 °C / min and hold for 5 h to obtain small-sized, single-phase titanium suboxide.

[0049] Example 4

[0050] The preparation method of the small-sized, single-phase titanium suboxide in this example is as follows:

[0051] (1) a. Dissolve 90 g of titanium dioxide in 11 M, 2 L of NaOH solution, stir to form a homogeneous colloid, and react at 110 °C for 36 h, then filter under pressure to obtain a precipitate; b. Wash the above precipitate until the solution pH = 12 ± 0.3; c. Add an acidic solution with a pH of 1 to the solution in step b to adjust the pH value of the solution to the pH value of the acidic solution used, aiming to displace the Na therein +, to form titanic acid, perform suction filtration, and then wash with water until pH≥5 to obtain NTA with a specific surface area of 380 m 2 / g.

[0052] (2) Control the mass ratio of NTA, sucrose, and distilled water to be 5:4:50, that is, disperse NTA (10 g) and sucrose (8 g) in distilled water (100 g), and shear with a shearing machine at a rate of 5000 r / min to obtain a precursor solution. Then pour the above precursor solution into a polytetrafluoroethylene high-pressure reaction kettle, and place the reaction kettle in an oven at a temperature of 180 °C for 15 h. After the reaction is completed, dry in a blast dryer at 80 °C to obtain a precursor powder.

[0053] (3) Place the precursor powder in a tubular furnace, introduce argon into the tubular furnace at a gas flow rate of 150 mL / min, and heat it to 1000 °C at a rate of 10 °C / min and hold for 3 h to obtain small-sized, single-phase titanium suboxide.

[0054] Example 5

[0055] The preparation method of the small-sized, single-phase titanium suboxide in this example is as follows:

[0056] (1) The specific preparation method of NTA is the same as that in step (1) of Example 4.

[0057] (2) Control the mass ratio of NTA, glucose, and distilled water to be 5:4:20, that is, disperse NTA (12.5 g) and sucrose (10 g) in distilled water (80 g), and shear with a shearing machine at a rate of 5000 r / min to obtain a precursor solution. Then pour the above precursor solution into a polytetrafluoroethylene high-pressure reaction kettle, and place the reaction kettle in an oven at a temperature of 180 °C for 15 h. After the reaction is completed, dry in a blast dryer at 80 °C to obtain a precursor powder.

[0058] (3) Place the precursor powder in a tubular furnace, introduce argon into the tubular furnace at a gas flow rate of 150 mL / min, and heat it to 1000 °C at a rate of 10 °C / min and hold for 3 h to obtain small-sized, single-phase titanium suboxide.

[0059] Example 6

[0060] The preparation method of the small-sized, single-phase titanium suboxide in this example is as follows:

[0061] (1) The specific preparation method of NTA is the same as that in step (1) of Example 4.

[0062] (2) Control the mass ratio of NTA, citric acid, and distilled water to be 5:4:35, that is, NTA (10 g, with a specific surface area of 380 m 2(g), Sucrose (8 g) was dispersed in distilled water (70 g), and sheared at a rate of 5000 r / min with a shearer to obtain a precursor solution. Then, the above precursor solution was poured into a polytetrafluoroethylene high-pressure reactor, and the reactor was placed in an oven at 180 °C for 15 h. After the reaction, it was dried in a blast dryer at 80 °C to obtain a precursor powder.

[0063] (3) The precursor powder was placed in a tubular furnace, and argon was introduced into the tubular furnace at a gas flow rate of 150 mL / min. It was heated to 1050 °C at a rate of 10 °C / min and held for 5 h to obtain small-sized, single-phase titanium suboxide.

[0064] Example 7

[0065] The preparation method of the small-sized, single-phase titanium suboxide in this example is as follows:

[0066] (1) a. 60 g of titanium dioxide was dissolved in 11 M, 2 L of NaOH solution, stirred to form a homogeneous colloid, and reacted at 110 °C for 36 h, then pressure-filtered to obtain a precipitate; b. The above precipitate was washed with water until the solution pH = 12 ± 0.3; c. An acidic solution with a pH of 1.2 was added to the solution in step b to adjust the pH value of the solution to the pH value of the acidic solution used, aiming to displace the Na + , to form titanic acid, then suction-filtered and washed with water until pH ≥ 5 to obtain NTA, with a specific surface area of 420 m 2 / g.

[0067] (2) Control the mass ratio of NTA, glucose, PEG 6000 to distilled water to be 5:0.1:0.9:30, that is, disperse NTA (10 g), sucrose (0.2 g), PEG 6000 (1.8 g) in distilled water (60 g), and shear at a rate of 10000 r / min with a shearer to obtain a precursor solution. Then, the above precursor solution was poured into a polytetrafluoroethylene high-pressure reactor, and the reactor was placed in an oven at 180 °C for 10 h. After the reaction, it was dried in a blast dryer at 80 °C to obtain a precursor powder.

[0068] (2) The precursor powder was placed in a tubular furnace, and argon was introduced into the tubular furnace at a gas flow rate of 150 mL / min. It was heated to 950 °C at a rate of 10 °C / min and held for 2 h to obtain small-sized, single-phase titanium suboxide.

[0069] Example 8

[0070] The preparation method of the small-sized, single-phase titanium suboxide in this example is as follows:

[0071] (1) The NTA prepared in step (1) of Example 1, with a surface area of 350 m 2 / g, was calcined at 500 °C for 5 h to obtain NTA-derived TiO 2 (with a specific surface area of 72 m 2 / g and the absolute value of Zeta potential being 20 mV).

[0072] (2) Control the mass ratio of NTA-derived TiO 2 , PEG 6000 and distilled water to be 2:1:15. First, disperse NTA-derived TiO 2 (10 g) and PEG 6000 (5 g) in distilled water (75 g), and shear at a rate of 10000 r / min with a shear machine to obtain a precursor solution. Then pour the above precursor solution into a polytetrafluoroethylene high-pressure reaction kettle, and place the reaction kettle in an oven at a temperature of 250 °C for 24 h. After the reaction is completed, dry it completely under vacuum at 60 °C to obtain a precursor powder.

[0073] (3) Place the precursor powder in a tubular furnace, heat it to 1050 °C at a rate of 10 °C / min and hold for 4 h to obtain small-sized, single-phase titanium suboxide.

[0074] Example 9

[0075] The preparation method of the small-sized, single-phase titanium suboxide in this example is as follows:

[0076] (1) The NTA prepared in step (1) of Example 4, with a surface area of 380 m 2 / g, was calcined at 650 °C for 4 h to obtain NTA-derived TiO 2 (with a specific surface area of 80 m 2 / g and the absolute value of Zeta potential being 21.6 mV).

[0077] (2) Control the mass ratio of NTA-derived TiO 2 , glucose and distilled water to be 1:1:10. First, disperse NTA-derived TiO 2 (10 g) and glucose (10 g) in distilled water (100 g), and shear at a rate of 10000 r / min with a shear machine to obtain a precursor solution. Then pour the above precursor solution into a polytetrafluoroethylene high-pressure reaction kettle, and place the reaction kettle in an oven at a temperature of 220 °C for 24 h. After the reaction is completed, dry it completely under vacuum at 60 °C to obtain a precursor powder.

[0078] (3) Place the precursor powder in a tube furnace, and introduce argon into the tube furnace at a gas flow rate of 150 mL / min. Heat it to 1050 °C at a rate of 10 °C / min and hold for 4 h to obtain small-sized, single-phase titanium suboxide.

[0079] Example 10

[0080] The preparation method of the small-sized, single-phase titanium suboxide in this example is as follows:

[0081] (1) Take the NTA prepared in step (1) of Example 7, with a specific surface area of 420 m 2 / g, and calcine it at 700 °C for 1 h to dehydrate and obtain NTA-derived TiO 2 (with a specific surface area of 75 m 2 / g and the absolute value of the Zeta potential being 23.9 mV).

[0082] (2) Control the mass ratio of NTA-derived TiO 2 , glucose, PEG 6000 to distilled water to be 10:1:5:85, that is, disperse NTA (10 g), sucrose (1 g), and PEG 6000 (5 g) in distilled water (85 g), and shear it with a shearing machine at a rate of 10000 r / min to obtain a precursor solution. Then pour the above precursor solution into a polytetrafluoroethylene high-pressure reaction kettle, and place the reaction kettle in an oven at 180 °C for 15 h. After the reaction is completed, dry it in a blast dryer at 80 °C to obtain the precursor powder.

[0083] (3) Place the precursor powder in a tube furnace, and introduce argon into the tube furnace at a gas flow rate of 150 mL / min. Heat it to 980 °C at a rate of 10 °C / min and hold for 4 h to obtain small-sized, single-phase titanium suboxide.

[0084] Example 11

[0085] The preparation method of the small-sized, single-phase titanium suboxide in this example is as follows:

[0086] (1) Take the NTA prepared in step (1) of Example 7, with a specific surface area of 420 m 2 / g, and calcine it at 600 °C for 2 h to dehydrate and obtain NTA-derived TiO 2 (with a specific surface area of 85 m 2 / g and the absolute value of the Zeta potential being 25 mV).

[0087] (2) Control the mass ratio of NTA-derived TiO 2 , PEG 6000, glucose to distilled water to be 5:1:3:30. First, 2(10 g), PEG 6000 (2 g) and glucose (6 g) were dispersed in distilled water (60 g), and sheared at a rate of 10000 r / min with a shearer to obtain a precursor solution. Then the above precursor solution was poured into a polytetrafluoroethylene high-pressure reactor, and the reactor was placed in an oven at 220 °C for 10 h. After the reaction, it was dried completely under vacuum at 60 °C to obtain an intermediate. Then the intermediate was redispersed in an aqueous glucose solution (containing 6 g of glucose and 60 g of distilled water). Then the above precursor solution was poured into a polytetrafluoroethylene high-pressure reactor, and the reactor was placed in an oven at 180 °C for 4 h. After the reaction, it was dried completely under vacuum at 60 °C to obtain a precursor powder.

[0088] (3) The precursor powder was placed in a tubular furnace, and argon was introduced into the tubular furnace at a gas flow rate of 150 mL / min, and the temperature was raised to 900 °C at a rate of 10 °C / min and held for 3 h to obtain small-sized, single-phase titanium suboxide.

[0089] Comparative example

[0090] The preparation method of titanium suboxide in this comparative example is as follows:

[0091] (1) The mass ratio of titanium dioxide (commercial titanium dioxide purchased from a certain company, specific surface area of 82 m 2 / g, crystal form is anatase, and the same crystal form and similar specific surface area as TiO 2 derived from NTA), PEG 6000, glucose and distilled water is 5:1:3:30. First, titanium dioxide (10 g), PEG 6000 (2 g) and glucose (6 g) were dispersed in distilled water (60 g), and sheared at a rate of 10000 r / min with a shearer to obtain a precursor solution. Then the above precursor solution was poured into a polytetrafluoroethylene high-pressure reactor, and the reactor was placed in an oven at 220 °C for 10 h. After the reaction, it was dried completely under vacuum at 60 °C to obtain an intermediate. Then the intermediate was redispersed in an aqueous glucose solution (containing 6 g of glucose and 60 g of distilled water). Then the above precursor solution was poured into a polytetrafluoroethylene high-pressure reactor, and the reactor was placed in an oven at 180 °C for 4 h. After the reaction, it was dried completely under vacuum at 60 °C to obtain a precursor powder.

[0092] (3) The precursor powder was placed in a tubular furnace, and argon was introduced into the tubular furnace at a gas flow rate of 150 mL / min, and the temperature was raised to 900 °C at a rate of 10 °C / min and held for 3 h.

[0093] Example of implementation effect

[0094] The crystal morphology, size, and phase composition of the prepared titanium suboxide were studied and analyzed, and the results are as follows.

[0095] Figure 1 is the NTA and NTA-derived TiO used in the present invention 2 SEM image. It can be seen from the figure that the particle size distribution of NTA-derived TiO 2 is uniform, and it retains the original tubular morphology of NTA, thus having a relatively high specific surface area. Additionally, due to the characteristics of one-dimensional materials, its morphology can still inhibit the sintering growth of particles.

[0096] Figure 2 is the FTIR spectrum of the NTA used in the present invention. It can be seen from the figure that there is a shoulder peak at 3200 cm -1 , indicating that NTA has abundant surface hydroxyl groups, and thus has good contact with organic carbon sources containing polar groups such as hydroxyl groups.

[0097] Figure 3 is the Zeta potential histogram of NTA-derived TiO 2 and titanium dioxide in the present invention. It can be seen from the figure that the absolute value of the Zeta potential of NTA-derived TiO 2 is greater than that of commercially available titanium dioxide, indicating that the former has better dispersibility in the system, is not easily sedimented, and the uniformity of the precursor for carbothermal reduction is better.

[0098] Figure 4 is the scanning electron micrograph of the precursor powder in the present invention, indicating that after hydrothermal treatment, the particles of the precursor maintain a relatively small particle size, which is beneficial for preparing small-sized titanium suboxide particles.

[0099] Figure 5 is the FTIR spectrum of the precursor powder in Example 11 of the present invention. It can be seen from the figure that by using NTA-derived TiO 2 carbon-carbon unsaturated bonds can be introduced into the carbothermal reduction system, providing more reduction electrons, thereby obtaining better reaction activity, which will be beneficial for obtaining single-phase titanium suboxide at a lower calcination temperature.

[0100] Figure 6 is the XRD spectrum of the product prepared in the present invention. Example 11 can obtain single-phase Ti 4 O 7 after reduction calcination at 900 °C.

[0101] Figure 7 is the SEM image of the nano-titanium suboxide powder prepared in Example 11 (a) and Comparative Example (b) of the present invention. It can be seen from the figure that the particle size of the product in the example is about 100 nm, and the particle size distribution is uniform and the average particle size is smaller than that of the comparative example.

[0102] In the present invention, NTA or its derivative TiO is used 2 and commercially available ordinary TiO 2 The results of the product appearance and phase composition are shown in Table 1

[0103] Table 1 Results of the size and phase composition of titanium suboxide prepared in the examples and comparative examples

[0104]

[0105]

[0106] As can be seen from Table 1, the present invention can prepare single-phase and small-sized titanium suboxide. And under the same calcination conditions, the prepared product is smaller than commercially available titanium dioxide. This is because by regulating the Ti / C combination, ratio and the amount of distilled water, more unsaturated bonds and reduction electrons can be introduced into the system, so that single-phase titanium suboxide can be obtained at a lower temperature. In addition, due to NTA and NTA-derived TiO 2 can react with the carbon source at the interface, such as the cracking and cross-linking polymerization of the polymer carbon source, so as to obtain a carbon thermal reduction precursor with a smaller particle size, which is beneficial to the synthesis of small-sized titanium suboxide

[0107] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention

Claims

1. A method for preparing small-sized, single-phase titanium oxide, characterized in that: Here are the steps: (1) dispersing a titanium source and a carbon source in water, and obtaining a precursor powder through a hydrothermal reaction; wherein the titanium source is titanate nanotubes or titanium dioxide derived from titanate nanotubes; (2) The precursor powder is calcined to obtain small-sized, single-phase titanium dioxide.

2. The method for preparing small-sized, single-phase titanium oxide according to claim 1, characterized in that: The specific surface area of ​​the titanate nanotubes in step (1) is 350-420 m 2 / g.

3. The method for preparing small-sized, single-phase titanium oxide according to claim 1, characterized in that: The titanium dioxide derived from titanate nanotubes in step (1) is obtained by calcining and dehydrating the titanate nanotubes.

4. The method for preparing small-sized, single-phase titanium oxide according to claim 3, characterized in that: The calcination and dehydration treatment is carried out at a temperature of 500-700°C and for a time of 1-5 h.

5. The method for preparing small-sized, single-phase titanium oxide according to any one of claims 1 to 4, characterized in that: In the step (1), the mass ratio of the titanium source, the carbon source and the distilled water is 1:(0.2-1):(4-10).

6. The method for preparing small-sized, single-phase titanium oxide according to claim 5, characterized in that: In the step (1), the carbon source is at least one of polyvinyl alcohol, polyethylene glycol, polyvinyl amide, glucose, sucrose and citric acid.

7. The method for preparing small-sized, single-phase titanium oxide according to claim 6, characterized in that: The temperature of the hydrothermal reaction in step (1) is 180-250° C. and the time is 8-24 h.

8. The method for preparing small-sized, single-phase titanium oxide according to claim 7, characterized in that: The calcination treatment in step (2) is carried out in an inert atmosphere, a reducing atmosphere or a combination of the two.

9. The method for preparing small-sized, single-phase titanium oxide according to claim 8, characterized in that: The calcination temperature in step (2) is 850-1050°C and the calcination time is 2-5 h.

10. Small-sized, single-phase titanium oxide prepared by the preparation method of claim 1.

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