Method for preparing titanium monoxide nanocrystalline through electron beam irradiation

Abstract

The invention relates to the technical field of irradiation chemistry and nano material preparation, in particular to a method for preparing titanium monoxide nanocrystals through electron beam irradiation. The method comprises the following steps: taking anatase type TiO2 as a raw material, and irradiating along a [010] crystal zone axis of the TiO2 by adopting an electron beam. According to the method, the electron beam is introduced to irradiate along the [010] crystal zone axis of the sample under the reduction action of the electron beam, and titanium dioxide is induced to be subjected to structural transformation and finally reduced to form titanium monoxide. According to the method for preparing the titanium monoxide nanocrystalline through electron beam irradiation, pollution caused by chemical synthesis and uncertainty of the size are reduced, operation is easy, cost is low, controllability is high, controllable preparation of nanoscale TiO in a specific selected area is achieved, manufacturing of a nanoscale TiO / TiO2 heterostructure can be achieved, and the method is suitable for industrial production. The method has important research value and wide application prospect in the fields of lithium-sulfur batteries, photocatalysis, nano sensors, superconduction and the like.

Description

Technical Field

[0001] The present invention relates to the technical fields of radiation chemistry and nanomaterial preparation, and particularly relates to a method for preparing titanium monoxide nanocrystals by electron beam irradiation. Background Art

[0002] Transition metal oxides with 3d electrons are naturally abundant on the earth, have strong stability and tunable electronic structures, and have very wide applications in the fields of superconductivity, supercapacitors, photocatalysis, electron transport, battery materials, sensors, etc. Their physical and chemical properties largely depend on the coordination environment of metal atoms, including oxidation state, coordination number, coordination structure, etc. Some transition metal oxides, such as TiO2, V2O, and MoO3, can be transformed into stable suboxides with different characteristics by changing the oxidation state of metal atoms through electron beam irradiation.

[0003] Electron beam irradiation is an advanced manufacturing process with high precision and is a commonly used tool for realizing surface modification and controllable generation of self-organized nanostructures. It is based on the interaction between the electron beam generated by an electron accelerator and matter. When a material is exposed to an electron beam, high-energy electrons will interact with the atoms in the material, forming elastic scattering or inelastic scattering, resulting in phenomena such as atomic defects, structural reconstruction, amorphization, or radiation reduction to improve the properties of the material or generate new materials. Its technology can be traced back to the early 20th century, when the interaction between electron beams and matter was mainly studied for the purpose of studying atomic structures. With the development of technology, electron beams with high energy beam current, high penetrability, high precision, and high efficiency have been applied in various aspects. For example, the wear resistance, corrosion resistance, conductivity, etc. of materials can be improved through electron beam irradiation; thin film materials with specific properties can be prepared; patterns with micro-nano scale precision and high resolution can be made, etc.

[0004] In recent years, the phase transformation of the maximum valence transition metal oxides induced by electron beam irradiation has also been deeply studied. For V2O5, WO3, TiO2, and Nb2O5, the corresponding suboxides based on the rock salt structure are detected as the final products. Among them, among various stable titanium suboxides, cubic titanium monoxide (TiO) is a very interesting material. It has very high hardness, good corrosion resistance, has the properties of titanium and oxygen atom vacancies, and contains a large amount (10-15 at%) of structural vacancies in each titanium and oxygen sublattice, making its oxygen index vary in the range of 0.75-1.25. This unique crystal structure makes it have extremely high electrical conductivity and excellent polarity, and can provide rich chemically adsorbed active sites, and has quite large application prospects in the fields of ceramics, superconductivity, lithium-sulfur batteries, capacitors, memristors, etc.

[0005] Currently, there are various methods for preparing titanium monoxide, such as molecular beam epitaxy, wet ball milling, chemical reduction, etc. However, these methods have complex processes, relatively harsh conditions, and the product purity is low, usually containing various sub-oxides of Ti (TiO x ). Electron beam irradiation is an advanced manufacturing process with high precision, which can directly achieve the controllable synthesis of products and is often used in the preparation and micro-mechanism research of MoO3, VO2, Fe2O3, etc. At present, there is an urgent need to provide a new method for preparing titanium monoxide (TiO) nanocrystals. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a method for preparing titanium monoxide nanocrystals by electron beam irradiation.

[0007] The method for preparing titanium monoxide nanocrystals by electron beam irradiation provided by the present invention can directly generate ordered cubic titanium monoxide on the parent titanium dioxide without using other chemical reagents, avoiding the low product purity and complex process of traditional preparation methods. This method has a simple operation process and strong controllability, and can realize the controllable preparation of target products by selecting different forms of starting raw materials and controlling the size and path of the electron beam. By controlling the size of the area irradiated by the electron beam, the preparation of TiO / TiO2 composite materials containing TiO can also be realized, thereby modifying titanium dioxide. Titanium dioxide has excellent optoelectronic properties, but as a wide-bandgap semiconductor (3.2 eV), it can only utilize about 3% of the total solar irradiance. Moreover, during the photocatalytic reaction process, the recombination rate of its photo-generated electrons and holes (10 -9 s) is much faster than the carrier capture rate (10 -7 ~10 -8 s), resulting in a low quantum efficiency. In addition, pure titanium dioxide has low inherent conductivity and relatively weak polarity, and its sulfur utilization rate and encapsulation of LiPSs are insufficient when chemically adsorbing the discharge product LiPSs, and the inhibition of the "shuttle effect" in lithium-sulfur batteries is very limited, seriously affecting the cycle efficiency and performance of the battery. When TiO with metal-like properties is combined with TiO2, a TiO / TiO2 heterojunction can be formed. Under different band structures, a spatial potential difference is formed on both sides of the heterojunction, inhibiting the recombination of photo-generated electrons and holes, effectively increasing the carrier lifetime, and accelerating charge transport, thereby improving the photocatalytic performance. The strong conductivity and polarity of TiO also enable Lewis acid-base to fully interact with each other to capture LiPSs, inhibit the shuttle effect, and significantly improve the cycle efficiency and life of lithium-sulfur batteries.

[0008] Specifically, the method for preparing titanium monoxide nanocrystals by electron beam irradiation provided by the present invention includes: using anatase TiO2 as a raw material and irradiating with an electron beam along the

[010] zone axis of the TiO2.

[0009] The present invention prepares TiO nanocrystals or composites containing TiO by means of electron beam irradiation reduction. The method of the present invention is characterized in that by utilizing the reduction effect of the electron beam, the electron beam is introduced through an electron microscope to irradiate along the

[010] zone axis of the sample, inducing the structural transformation of titanium dioxide and finally reducing it to form titanium monoxide. This method is based on the interaction between the electron beam and the material, reducing the pollution and size uncertainty caused by chemical synthesis, with simple operation, low cost and strong controllability, and can realize the controllable preparation of nanoscale TiO in a specific selected area, and can also realize the fabrication of nanoscale TiO / TiO2 heterostructures, which has important research value and broad application prospects in the fields of lithium-sulfur batteries, photocatalysis, nanosensors, superconductivity, etc.

[0010] Preferably, the anatase TiO2 is a single material such as nanoparticles, nanowires, nanobelts, nanotubes or thin films, or a composite material such as nanoparticles, nanowires, nanobelts, nanotubes or thin films containing anatase TiO2 tissues.

[0011] As a preference, the method for preparing titanium monoxide nanocrystals by the above-mentioned electron beam irradiation includes:

[0012] 1) Select anatase TiO2 nanoparticles as raw materials, mix the TiO2 nanoparticles with deionized water to obtain a TiO2 suspension;

[0013] 2) Coating the TiO2 suspension on a support grid and then drying it;

[0014] 3) Placing the obtained thin film on a double-tilt sample holder of an electron microscope, adjusting the sample zone axis to the

[010] zone axis, and irradiating the selected area of the sample with an electron beam current under an acceleration voltage to convert TiO2 into TiO.

[0015] Preferably, in step 1), the TiO2 and deionized water are ultrasonically dispersed for 20 - 30 min.

[0016] Preferably, in step 2), the support grid is an ultra-thin carbon film copper grid, a carbon film copper grid or a microgrid.

[0017] More preferably, in step 2), the drying is carried out by baking at a temperature of 40 - 90 °C for 0.5 - 2 h.

[0018] As a preference, the acceleration voltage is 50 - 600 kV, preferably 80 - 300 kV, and more preferably 200 - 300 kV.

[0019] Preferably, the sample in the selected area is irradiated with an electron beam current of 11-68 pA for 5-100 min; more preferably, the sample in the selected area is irradiated with an electron beam current of 23-35 pA for 10-40 min.

[0020] In a second aspect, the present invention provides a TiO nanocrystal or a composite material containing TiO prepared by any of the above methods for preparing titanium monoxide nanocrystals by electron beam irradiation.

[0021] In a third aspect, the present invention provides the application of any of the above methods for preparing titanium monoxide nanocrystals by electron beam irradiation in the preparation of lithium-sulfur batteries, photocatalysts, nanosensors, and superconducting materials.

[0022] The beneficial effects of the present invention are at least as follows: (1) The preparation process of the present invention is simple. In this experiment, a one-step reaction is used. Only the raw materials need to be loaded onto the specimen grid and then placed into a transmission electron microscope or a scanning electron microscope; (2) The production cost is relatively low. No other materials are required during the preparation process, and the price of TiO2 powder is cheap, which can save a certain amount of production cost; (3) The product purity is high. No other chemical reagents are introduced during the production process, and there is no impurity residue in the product. (4) High repeatability. The success rate of preparing TiO nanocrystals according to this method is high, and strict process condition control is not required; (5) Strong controllability. The size and position of the TiO region processed and prepared by the present invention are controllable. The processing size and position are determined by the electron beam scanning range, and nano-scale processing can be achieved; (6) Short growth cycle. From loading the sample to reacting and finally sampling, this method only takes half an hour, with less time consumption. Description of the Drawings

[0023] 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. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 (a) 50-200 nm TiO2 nanoparticles and (b) X-ray diffraction pattern of the nanoparticles provided by the embodiments of the present invention;

[0025] Figure 2 Transmission electron microscope (STEM) images of (a) TiO2 and (b) TiO nanocrystals prepared by electron beam irradiation provided by the embodiments of the present invention;

[0026] Figure 3(a) A series of process images of the conversion of anatase TiO₂ to TiO along the

[010] zone axis under 300 kV and (b) their corresponding FFT signals provided by the embodiments of the present invention;

[0027] Figure 4 (a) The FFT signals of the selected area during the transformation process and (b) the simulated electron diffraction patterns provided by the embodiments of the present invention;

[0028] Figure 5 (a) The contour map of the in-situ EELS profile and (b) the representative EELS spectra recorded at different times provided by the embodiments of the present invention;

[0029] Figure 6 A series of process images of the conversion of anatase TiO₂ to TiO along the

[010] zone axis under 200 kV by continuous irradiation of the electron beam provided by the embodiments of the present invention;

[0030] Figure 7 A series of chronological process images of the conversion of anatase TiO₂ to TiO along the

[010] zone axis under 80 kV by continuous irradiation of the electron beam provided by the embodiments of the present invention;

[0031] Figure 8 A series of chronological process images of the continuous irradiation of the electron beam along the

[110] zone axis of anatase TiO₂ under 300 kV provided by the comparative examples of the present invention;

[0032] Figure 9 A series of chronological process images of the continuous irradiation of the electron beam along the [-120] zone axis of anatase TiO₂ under 300 kV provided by the comparative examples of the present invention;

[0033] Figure 10 A series of chronological process images of the continuous irradiation of the electron beam along the [13-1] zone axis of anatase TiO₂ under 300 kV provided by the comparative examples of the present invention. Detailed implementation manners

[0034] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present invention belong to the scope of protection of the present invention.

[0035] In the embodiments of the present invention, for those without specific technologies or conditions noted, they shall follow the technologies or conditions described in the literature in this field or the product specifications. For those devices, instruments, reagents, etc. without the noted manufacturers, they are all conventional products that can be obtained through regular channels. The raw materials used in the present invention can be conveniently purchased in the domestic product market.

[0036] Example 1

[0037] 1) Select 100nm TiO2 nanoparticle material.

[0038] 2) Dissolve 10mg of the above TiO2 powder in 1mL of deionized water, and ultrasonically disperse it for 20 minutes until it is evenly mixed to form a TiO2 suspension.

[0039] 3) Use a 0.5mL glass spotting capillary to suck up the above suspension, drop it on a copper mesh support with an ultrathin carbon film, and then place it in an oven at 70°C for baking for 2 hours to obtain a thin film.

[0040] 4) Place the support processed in step 3) on a transmission electron microscope double-tilt sample holder, adjust the sample zone axis to the

[010] zone axis, and irradiate the sample in the selected area with an electron beam current of 35pA for 40 minutes at an acceleration voltage of 300kV to convert TiO2 into TiO.

[0041] 5) After the electron beam irradiation is completed, take out the support.

[0042] Test the TiO prepared in Example 1, and the test results are as Figures 1-5 shown, Figure 1 showing (a) 50 - 200nm TiO2 nanoparticles and (b) the X-ray diffraction data of the nanoparticles, proving that it has good crystallinity and is of the anatase type. Figure 2 showing (a) transmission electron microscope (STEM) pictures of TiO2 and (b) TiO nanocrystals prepared by electron beam irradiation. The marked interplanar spacings in the figure are respectively and consistent with the lattice spacings of the TiO2 {004} crystal plane family and the TiO {002} crystal plane family. Figure 3 The marked interplanar spacings in are respectively and Figure 3 consistent with the lattice spacings of the TiO2 {004} crystal plane family and the TiO {002} crystal plane family, Figure 4 showing (a) a series of process images of the conversion of anatase TiO2 along the

[010] zone axis into TiO under continuous irradiation at 300kV, and (b) its corresponding FFT signal confirming this conversion process and the final product being TiO. Figure 4It shows (a) the FFT signal of the selected area during the transformation process, which contains two sets of aligned diffraction points, being the same as (b) the simulated electron diffraction pattern, demonstrating the existence of a good heteroepitaxial relationship between the newly formed TiO and the parent TiO2. Figure 5 It shows (a) the contour map of the in-situ EELS profile. (b) Representative EELS spectra recorded at different times. The characteristic peak Ti-L in the figure 3,2 gradually shifts to the left, differing from the initial position by approximately 2 eV, while O-K remains basically unchanged, proving that the valence state of Ti gradually changes from +4 to +2 during irradiation, that is, TiO2 is transformed into TiO.

[0043] Example 2

[0044] 1) Select 50 nm TiO2 nanoparticle material.

[0045] 2) Dissolve 10 mg of the above TiO2 powder in 1 mL of deionized water, and ultrasonically disperse it for 20 minutes until it is evenly mixed to form a TiO2 suspension.

[0046] 3) Use a 0.5 mL glass spotting capillary to suck up the above suspension, drop it on a copper mesh support with an ultrathin carbon film, and then place it in an oven at 70 °C for baking for 2 hours to obtain a thin film.

[0047] 4) Place the support processed in step 3) on a double-tilt sample holder of a transmission electron microscope, adjust the sample zone axis to the

[010] zone axis, and irradiate the selected area of the sample with an electron beam current of 23 pA for 15 minutes at an acceleration voltage of 200 kV to transform TiO2 into TiO.

[0048] 5) After the electron beam irradiation is completed, take out the support.

[0049] Figure 6 It shows a series of process images of the transformation of anatase TiO2 along the

[010] zone axis into TiO under 200 kV electron beam irradiation. Compared with Example 1, the thickness of the TiO nanocrystals formed in this example is uneven, and more pits caused by irradiation damage will be formed on the surface.

[0050] Example 3

[0051] 1) Select 50 nm TiO2 nanoparticle material.

[0052] 2) Dissolve 10 mg of the above TiO2 powder in 1 mL of deionized water, and ultrasonically disperse it for 20 minutes until it is evenly mixed to form a TiO2 suspension.

[0053] 3) Use a 0.5 mL glass spotting capillary to suck up the above suspension, drop it on a copper mesh support with an ultrathin carbon film, and then place it in an oven at 70 °C for baking for 2 hours to obtain a thin film.

[0054] 4) Place the thin film on the carrier grid processed in step 3) on a double-tilt sample holder of a transmission electron microscope. Adjust the sample zone axis to the

[010] zone axis. At an acceleration voltage of 80 kV, irradiate the selected area of the sample with an electron beam current of 11 pA for 16 minutes to convert TiO₂ into TiO.

[0055] 5) After the electron beam irradiation is completed, take out the carrier grid.

[0056] Figure 7 A series of process images of the conversion of anatase TiO₂ along the

[010] zone axis by continuous electron beam irradiation at 80 kV in chronological order (a-f are 0 s, 217 s, 485 s, 726 s, 814 s, 982 s respectively) are shown. Compared with the TiO nanocrystals with uneven thickness and low integrity formed in Examples 1 and 2, partial voids will be formed on the surface.

[0057] Comparative Example 1

[0058] 1) Select 50 nm TiO₂ nanoparticle materials.

[0059] 2) Dissolve 10 mg of the above TiO₂ powder in 1 mL of deionized water and ultrasonically disperse it for 20 minutes until it is uniformly mixed to form a TiO₂ suspension.

[0060] 3) Use a 0.5 mL glass spotting capillary to suck up the above suspension, drop it on a carrier grid of an ultra-thin carbon film copper mesh, and then place it in an oven at 70 °C for baking for 2 hours to obtain a thin film.

[0061] 4) Place the carrier grid processed in step 3) on a double-tilt sample holder of a transmission electron microscope. Adjust the sample zone axis to the

[110] zone axis. At an acceleration voltage of 300 kV, irradiate the selected area on two particle samples with an electron beam current of 35 pA for 2 - 4 minutes to cause a structural change in TiO₂.

[0062] 5) After the electron beam irradiation is completed, take out the carrier grid.

[0063] Figure 8 A series of process images of the continuous electron beam irradiation along the

[110] zone axis of anatase TiO₂ at 300 kV in chronological order (a-d are 0 s of particle 1, 143 s, 0 s of particle 2, and 215 s respectively) are shown. Compared with the TiO nanocrystals with cubic lattices formed after irradiation in Examples 1, 2, and 3, only irradiation damage voids and amorphous products can be formed after irradiation in this direction. The STEM image corresponding FFT signal does not show new diffraction spots, indicating that no new crystal structure is generated.

[0064] Comparative Example 2

[0065] 1) Select 50 nm TiO2 nanoparticle material.

[0066] 2) Dissolve 10 mg of the above TiO2 powder in 1 mL of deionized water, and ultrasonically disperse for 20 minutes until it is evenly mixed to form a TiO2 suspension.

[0067] 3) Use a 0.5 mL glass spotting capillary to suck up the above suspension, drop it on a copper mesh carrier with an ultrathin carbon film, and then place it in an oven at 70 °C for 2 hours to obtain a film.

[0068] 4) Place the carrier processed in step 3) on a transmission electron microscope double-tilt sample holder, adjust the sample zone axis to the [-120] zone axis, and irradiate the selected area of the sample with an electron beam current of 35 pA at an acceleration voltage of 300 kV for 12 minutes to change the TiO2 structure.

[0069] 5) After the electron beam irradiation is completed, take out the carrier.

[0070] Figure 9 A series of process images of electron beam irradiation along the [-120] zone axis of anatase TiO2 at 300 kV in chronological order (a-d are 0 s, 178 s, 364 s, and 672 s respectively) are shown. Compared with the TiO nanocrystals with cubic lattices formed after irradiation in Examples 1, 2, and 3, a large number of amorphous products and some irradiation damage pits are formed after irradiation in this direction. The corresponding FFT signal of its STEM image does not show new diffraction spots, indicating that no new crystal structure is generated.

[0071] Comparative Example 3

[0072] 1) Select 50 nm TiO2 nanoparticle material.

[0073] 2) Dissolve 10 mg of the above TiO2 powder in 1 mL of deionized water, and ultrasonically disperse for 20 minutes until it is evenly mixed to form a TiO2 suspension.

[0074] 3) Use a 0.5 mL glass spotting capillary to suck up the above suspension, drop it on a copper mesh carrier with an ultrathin carbon film, and then place it in an oven at 70 °C for 2 hours to obtain a film.

[0075] 4) Place the carrier processed in step 3) on a transmission electron microscope double-tilt sample holder, adjust the sample zone axis to the [13-1] zone axis, and irradiate the selected area of the sample with an electron beam current of 35 pA at an acceleration voltage of 300 kV for 10 minutes to change the TiO2 structure.

[0076] 5) After the electron beam irradiation is completed, take out the carrier.

[0077] Figure 10A series of process images of the continuous irradiation of the electron beam along the [13-1] zone axis of anatase TiO2 at 300 kV are shown, arranged chronologically (a-d are 0 s, 178 s, 364 s, and 672 s respectively). Compared with the TiO nanocrystals with cubic lattices formed after irradiation in Examples 1, 2, and 3, only irradiation damage cavities and amorphous products can be formed after irradiation in this direction, and the corresponding FFT signals of its STEM images do not show new diffraction spots, indicating that no new crystal structure is generated.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing titanium monoxide nanocrystals by electron beam irradiation, characterized in that, It includes using anatase TiO₂ as the raw material and irradiating it with an electron beam along the [010] zone axis of the TiO₂.

2. The method for preparing titanium monoxide nanocrystals by electron beam irradiation according to claim 1, characterized in that, The anatase TiO₂ is a single-element material in the form of nanoparticles, nanowires, nanobelts, nanotubes or thin films, or a composite material containing anatase TiO₂ tissues in the form of nanoparticles, nanowires, nanobelts, nanotubes or thin films.

3. The method for preparing titanium monoxide nanocrystals by electron beam irradiation according to claim 2, wherein, It includes: 1) Select anatase TiO₂ nanoparticles as the raw material, mix the TiO₂ nanoparticles with deionized water to obtain a TiO₂ suspension; 2) Coating the TiO₂ suspension on a specimen grid and then drying it; 3) Placing the obtained thin film on a double-tilt specimen holder of an electron microscope, adjusting the sample zone axis to the [010] zone axis, and irradiating the selected area of the sample with an electron beam current at an accelerating voltage to convert TiO₂ into TiO.

4. The method for preparing titanium monoxide nanocrystals by electron beam irradiation according to claim 3, wherein, In step 1), TiO₂ and deionized water are ultrasonically dispersed for 20 - 30 min.

5. The method for preparing titanium monoxide nanocrystals by electron beam irradiation according to claim 3, wherein In step 2), the specimen grid is an ultrathin carbon film copper grid, a carbon film copper grid or a microgrid.

6. The method for preparing titanium monoxide nanocrystals by electron beam irradiation according to claim 3, wherein In step 2), the drying is carried out by baking at a temperature of 40 - 90 °C for 0.5 - 2 h.

7. The method for preparing titanium monoxide nanocrystals by electron beam irradiation according to any one of claims 1-6, characterized in that, The accelerating voltage is 50 - 600 kV, preferably 80 - 300 kV, and more preferably 200 - 300 kV.

8. The method for preparing titanium monoxide nanocrystals by electron beam irradiation according to any one of claims 1-6, characterized in that, Irradiate the selected area of the sample with an electron beam current of 11 - 68 pA for 5 - 100 min; preferably, irradiate the selected area of the sample with an electron beam current of 23 - 35 pA for 10 - 40 min.

9. TiO nanocrystals or composite materials containing TiO prepared by the method for preparing titanium monoxide nanocrystals by electron beam irradiation according to any one of claims 1 - 8.

10. Application of the method for preparing titanium monoxide nanocrystals by electron beam irradiation according to any one of claims 1 - 8 in the preparation of lithium-sulfur batteries, photocatalysts, nanosensors, superconducting materials.

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