Preparation and application of high-refractive-index barium titanate nanofiller for nanoimprint process

Abstract

The invention discloses preparation and application of a high-refractive-index barium titanate nanofiller for a nanoimprint process, and the preparation method comprises the following steps: adding barium hydroxide octahydrate into a solvent, ultrasonically mixing uniformly, then adding titanium dioxide, and continuously performing ultrasonic treatment to obtain a mixed solution; transferring the mixed solution into a reactor for solvothermal reaction, naturally cooling, taking out, standing for layering, removing supernate, washing and filtering the residual solid-liquid mixture, and drying to obtain the high-refractive-index barium titanate nanofiller for the nanoimprint process. The invention develops a preparation method of a high-refractive-index barium titanate nanofiller for a nanoimprint process. A solvothermal method is used for preparing the high-purity and nearly spherical barium titanate nanofiller with the particle size of 1t; the BaTiO3 nanofiller with the refractive index of 30 nm can be applied to a nanoimprint process, and a new material solution of a high-refractive-index coating is provided for diffraction optical waveguides of AR (Augmented Reality) glasses.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nano-barium titanate preparation, and more particularly, relates to a preparation and application of high-refractive nano-barium titanate filler for a nano-imprint process. BACKGROUND

[0002] Augmented reality (AR) devices are considered as the core entrance of human-computer interaction in the artificial intelligence era, and the development trend of light and thin and integration of AR glasses puts forward unprecedentedly harsh requirements on optical coating: while ensuring low scattering and low haze, it must achieve an ultra-high refractive index of >2.3 in the visible-near infrared band to meet the coupling efficiency and field angle expansion requirements of the diffractive optical waveguide. The traditional high-refractive filler system mainly uses metal oxides such as TiO2, ZrO2 and ZnO, and the refractive index is mostly limited in the range of 2.0-2.2, which has been difficult to meet the extreme pursuit of "thinner, lighter and higher refractive index" of the next generation of AR optical systems.

[0003] Barium titanate (BaTiO3) is considered as an ideal candidate to break through the bottleneck of traditional fillers due to its perovskite crystal structure and strong electronic polarization characteristics, and the refractive index of the bulk material can reach 2.4, which is significantly better than existing oxide systems. However, to apply BaTiO3 to the nano-imprint process, it must achieve the following at the same time: particle size <30 nm and extremely narrow distribution to avoid light scattering; high crystallinity and tetragonal phase stability to ensure high refractive index; surface functionalization for compatibility with UV-curable resins. Although the traditional solid-phase method for preparing barium titanate is mature, the calcination temperature is high (>1100 ℃) and the particle size is large (>500 nm), which is difficult to meet the stringent requirements of ultra-thin dielectric layers on powder particle size (<30 nm) and dispersibility. Solvothermal method is considered as one of the ideal routes for preparing nano-barium titanate due to its low reaction temperature (150-250 ℃), low energy consumption, high product crystallinity and controllable morphology. SUMMARY

[0004] An object of the present application is to solve at least the above problems and / or defects, and to provide at least the advantages to be explained later.

[0005] To achieve these objects and other advantages of the present application, a method for preparing high-refractive nano-barium titanate filler for a nano-imprint process is provided, comprising the following steps: Step one, ultrasonically mix the barium hydroxide octahydrate into the solvent until it is uniformly mixed, then add titanium dioxide and continue to ultrasonically mix, to obtain a mixed solution; Step two, transfer the mixed solution into a reactor for solvothermal reaction, and after natural cooling, take out and stand for stratification, then remove the supernatant, and wash and filter the remaining solid-liquid mixture, and dry it to obtain the high-refractive nano-barium titanate filler for the nano-imprint process.

[0006] Preferably, in step one, the molar ratio of barium hydroxide octahydrate to titanium dioxide is 0.9~1.2:1.

[0007] Preferably, in step one, the solvent is one or more of ethylene glycol methyl ether, anhydrous ethanol, and ethylene glycol.

[0008] Preferably, when the solvent is ethylene glycol methyl ether and anhydrous ethanol, the volume ratio of ethylene glycol methyl ether to anhydrous ethanol is 10~20:20~30; When the solvent is ethylene glycol and anhydrous ethanol, the volume ratio of ethylene glycol to anhydrous ethanol is 10~20:20~30; When the solvent is ethylene glycol methyl ether and ethylene glycol, the volume ratio of ethylene glycol methyl ether to ethylene glycol is 10~20:20~30; When the solvent is ethylene glycol methyl ether, anhydrous ethanol, and ethylene glycol, the volume ratio of ethylene glycol methyl ether, anhydrous ethanol, and ethylene glycol is 5~15:15~25:5~10.

[0009] Preferably, in step one, the mass-to-volume ratio of barium hydroxide octahydrate to solvent is 2-4 g: 30-50 mL.

[0010] Preferably, in step one, the ultrasonic power is 200~500W, the frequency is 40~70kHz, the ultrasonic mixing time is 10~60min, and the ultrasonic treatment continues for 10~60min.

[0011] Preferably, in step two, the solvothermal reaction temperature is 150~250℃ and the reaction time is 6~20h.

[0012] Preferably, in step two, the plant is left to stand for 0.5 to 3 hours; the drying temperature is 50 to 70°C.

[0013] Preferably, step two is replaced by: subjecting the mixed solution to a high-voltage pulsed electric field treatment, then transferring it to a reactor for a solvothermal reaction, allowing it to cool naturally and then removing it for static treatment while simultaneously applying a high-voltage pulsed electric field, then allowing it to stand and separate into layers, removing the supernatant, and washing, filtering, and drying the remaining solid-liquid mixture to obtain a high-refractive-index barium titanate nanofiller for nanoimprinting.

[0014] Preferably, the electric field strength of the high-voltage pulse electric field is 10~50 kV / cm, the frequency is 100~500 Hz, and the processing time is 3~15 min.

[0015] Application of a high-refractive-index barium titanate nanofiller prepared by the method described above in nanoimprinting process.

[0016] The present invention has at least the following beneficial effects: It develops a method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes. Using a solvothermal method with barium hydroxide and titanium dioxide as raw materials, and by adjusting the raw material ratio and optimizing the solvent system, high-purity, near-spherical barium titanate nanofillers with a particle size <30 nm are prepared. These nanofillers can be used in nanoimprinting processes, providing a new material solution for high-refractive-index coatings for diffractive waveguides in AR glasses. Furthermore, the present invention combines a high-voltage pulsed electric field to further improve the preparation efficiency, resulting in barium titanate nanofillers with higher purity, smaller particle size, and narrower particle size distribution. The preparation method of the present invention is simple and conducive to large-scale industrial production.

[0017] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0018] Figure 1 SEM images of the barium titanate nanofillers prepared in Examples 1-2, showing the microstructure and corresponding particle size distribution: (ab) BaTiO3-1a, (cd) BaTiO3-1b. Figure 2 The SEM images show the barium titanate nanofillers prepared in Examples 3-4 and their corresponding particle size distributions: (ef)BaTiO3-2a, (gh)BaTiO3-2b. Figure 3 FT-IR images of barium titanate nanofillers prepared in Examples 1-4; Figure 4 XRD patterns of barium titanate nanofillers prepared in Examples 1-4; Figure 5 XPS spectra of barium titanate nanofillers prepared in Examples 1 and 3: (a) full spectrum, (b) Ba 3d, (c) Ti 2p, (d) O 1s; Figure 6 This is a TEM image of the barium titanate nanofiller prepared in Example 3. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0020] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0021] Example 1 A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes includes the following steps: Step 1: Weigh 3.155g Ba(OH)2·8H2O into 40 mL of anhydrous ethanol and sonicate for 30 min to mix thoroughly. Then add 0.8g of titanium dioxide and continue sonicating for 30 min to obtain a mixed solution. The sonication power is 300 W and the frequency is 55 kHz. Step 2: Pour the mixed solution into a polytetrafluoroethylene liner and react at a solvothermal reaction temperature of 200℃ for 18 h. After natural cooling, remove the solution and let it stand for 2 h to separate into layers. Then, use a dropper to remove the supernatant. After removing the supernatant, wash and filter the solid-liquid mixture with anhydrous ethanol and deionized water, and then dry it in a drying oven at 60℃. The high refractive index barium titanate nanofiller obtained for nanoimprinting process is denoted as BaTiO3-1a.

[0022] Example 2 A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes includes the following steps: Step 1: Weigh 3.47g Ba(OH)2·8H2O and sonicate it in 40 mL of anhydrous ethanol for 30 min until it is homogeneous. Then add 0.8g titanium dioxide and continue sonicating for 30 min to obtain a mixed solution. The sonication power is 300 W and the frequency is 55 kHz. Step 2: Pour the mixed solution into a polytetrafluoroethylene inner liner and react at a solvothermal reaction temperature of 200℃ for 18 h. After natural cooling, remove the mixture and let it stand for 2 h to separate into layers. Then, use a dropper to remove the supernatant. The solid-liquid mixture after removing the supernatant is washed and filtered with anhydrous ethanol and deionized water and then dried in a drying oven at 60℃. The high refractive index barium titanate nanofiller used in the nanoimprinting process is denoted as BaTiO3-1b.

[0023] Example 3 A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes includes the following steps: Step 1: Weigh 3.155g Ba(OH)2·8H2O into a mixture of 16 mL ethylene glycol methyl ether and 24 mL anhydrous ethanol, and sonicate for 30 min to mix thoroughly. Then add 0.8 g titanium dioxide and continue sonicating for 30 min to obtain a mixed solution. The sonication power is 300 W and the frequency is 55 kHz. Step 2: Pour the mixed solution into a polytetrafluoroethylene inner liner and react at a solvothermal reaction temperature of 200℃ for 18 h. After natural cooling, remove the mixture and let it stand for 2 h to separate into layers. Then, use a dropper to remove the supernatant. The solid-liquid mixture after removing the supernatant is washed and filtered with anhydrous ethanol and deionized water and then dried in a drying oven at 60℃. The high refractive index barium titanate nanofiller used in the nanoimprinting process is denoted as BaTiO3-2a.

[0024] Example 4 A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes includes the following steps: Step 1: Weigh 3.47g Ba(OH)2·8H2O into a mixture of 16 mL ethylene glycol methyl ether and 24 mL anhydrous ethanol, and sonicate for 30 min to mix thoroughly. Then add 0.8g titanium dioxide and continue sonicating for another 30 min to obtain a mixed solution. The sonication power is 300 W and the frequency is 55 kHz. Step 2: Pour the mixed solution into a polytetrafluoroethylene inner liner and react at a solvothermal reaction temperature of 200℃ for 18 h. After natural cooling, remove the mixture and let it stand for 2 h to separate into layers. Then, use a dropper to remove the supernatant. After removing the supernatant, wash and filter the solid-liquid mixture with anhydrous ethanol and deionized water, and then dry it in a drying oven at 60℃. The high refractive index barium titanate nanofiller obtained for nanoimprinting process is denoted as BaTiO3-2b.

[0025] Figures 1-2 The images show the SEM microstructure and corresponding particle size distribution of the barium titanate nanofillers prepared in Examples 1-4: (ab) BaTiO3-1a, (cd) BaTiO3-1b, (ef) BaTiO3-2a, and (gh) BaTiO3-2b. Statistical analysis of the BaTiO3 nanoparticles prepared by different methods shows that the average particle size of the barium titanate particles is concentrated in the range of 24.8-28.3 nm, with BaTiO3-1b having the smallest average particle size. However, both BaTiO3-1 samples showed relatively obvious rod-shaped impurities in their SEM images, which may be unreacted nano-TiO2 from the raw materials. In contrast, this was not observed in the SEM images of the two BaTiO3-2 samples. Therefore, it is preliminarily concluded that the method for preparing BaTiO3-2 is more conducive to the preparation of high-purity barium titanate nanospheres.

[0026] Figure 3 FT-IR images of the barium titanate nanofillers prepared in Examples 1-4. (Image taken at 575 cm⁻¹) -1 The strong absorption peak appearing nearby corresponds to the Ti-O bending vibration in BaTiO3, at 3420 cm⁻¹. -1 The nearby broad peak and 1635 cm -1The nearby peaks can be attributed to the stretching vibrations of hydroxyl groups caused by the absorption of moisture from the air by the sample.

[0027] Figure 4 The XRD patterns of the barium titanate nanofillers prepared in Examples 1-4 are shown. The figures show that all four samples exhibit good crystallinity, corresponding to a cubic (PDF#01-075-0213) perovskite structure. All diffraction peaks of the BaTiO3-2 samples match the corresponding positions on the standard card. However, the XRD patterns of the BaTiO3-1 samples show a small number of impurity peaks that match the titanium dioxide (PDF#01-070-2556) standard card, indicating the presence of unreacted TiO2 impurities in the two BaTiO3-1 samples.

[0028] Figure 5 XPS spectra of the barium titanate nanofillers prepared in Examples 1 and 3: (a) full spectrum, (b) Ba 3d, (c) Ti 2p, (d) O 1s. All corresponding elements can be observed, indicating successful synthesis of the material. In the Ba 3d spectrum of BaTiO3-1a, the two peaks with binding energies at 778.16 eV and 779.46 eV correspond to Ba 3d. 5 / 2 The two peaks at 793.51 eV and 794.97 eV correspond to Ba 3d 3 / 2 In the Ti 2p spectrum, the two peaks with binding energies at 457.74 eV and 463.44 eV correspond to Ti 2p orbitals, respectively. 3 / 2 Orbits and Ti 2p 1 / 2 In the O 1s spectrum, the two peaks with binding energies of 528.86 eV and 531.36 eV are attributed to lattice oxygen and hydroxyl oxygen, respectively. In the Ba 3d spectrum of BaTiO3-2a, the two peaks with binding energies of 778.28 eV and 779.39 eV correspond to Ba 3d orbitals. 5 / 2 The two peaks at 793.59 eV and 794.69 eV correspond to Ba 3d 3 / 2 In the Ti 2p spectrum, the two peaks with binding energies at 457.63 eV and 463.36 eV correspond to Ti 2p orbitals, respectively. 3 / 2 Orbits and Ti 2p 1 / 2 In the O 1s orbital spectrum, the two peaks with binding energies at 528.33 eV and 531.02 eV are attributed to lattice oxygen and hydroxyl oxygen, respectively.

[0029] Figure 6 This is a TEM image of the barium titanate nanofiller prepared in Example 3. TEM allows for a clearer observation of the morphology and size of BaTiO3-2a.Figure 6 In (c), several barium titanate particles approximately 20 nm in size can be clearly seen. In BaTiO3-2a, lattice fringes of 0.286 nm were detected. Figure 6 (d)), which corresponds to the (110) crystal plane of BaTiO3.

[0030] Example 5 A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes includes the following steps: Step 1: Weigh 3.155g Ba(OH)2·8H2O into 40 mL of ethylene glycol methyl ether and sonicate for 30 min to mix thoroughly. Then add 0.8g of titanium dioxide and continue sonicating for 30 min to obtain a mixed solution. The sonication power is 300 W and the frequency is 55 kHz. Step 2: Pour the mixed solution into a polytetrafluoroethylene liner and react at a solvothermal reaction temperature of 200℃ for 18 h. After natural cooling, remove the solution and let it stand for 2 h to separate into layers. Then, use a dropper to remove the supernatant. After removing the supernatant, wash and filter the solid-liquid mixture with anhydrous ethanol and deionized water, and then dry it in a drying oven at 60℃. The high refractive index barium titanate nanofiller used in the nanoimprinting process is denoted as BaTiO3-3a. Compared to Example 3, this example uses ethylene glycol methyl ether as a solvent; the barium titanate nanofiller prepared in this example has a particle size of 28.5 nm and contains unreacted TiO2 impurities.

[0031] Example 6 A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes includes the following steps: Step 1: Weigh 3.155g Ba(OH)2·8H2O into 40 mL of ethylene glycol and sonicate for 30 min to mix thoroughly. Then add 0.8g of titanium dioxide and continue sonicating for 30 min to obtain a mixed solution. The sonication power is 300 W and the frequency is 55 kHz. Step 2: Pour the mixed solution into a polytetrafluoroethylene liner and react at a solvothermal reaction temperature of 200℃ for 18 h. After natural cooling, remove the solution and let it stand for 2 h to separate into layers. Then, use a dropper to remove the supernatant. After removing the supernatant, wash the solid-liquid mixture with anhydrous ethanol and deionized water, filter it, and dry it in a drying oven at 60℃. The high refractive index barium titanate nanofiller used in the nanoimprinting process is denoted as BaTiO3-4a. Compared to Example 3, this example uses ethylene glycol as a solvent; the barium titanate nanofiller prepared in this example has a particle size of 29.6 nm and contains unreacted TiO2 impurities.

[0032] Example 7 A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes includes the following steps: Step 1: Weigh 3.155g Ba(OH)2·8H2O into a mixed solution of 16 mL ethylene glycol and 24 mL anhydrous ethanol, and sonicate for 30 min to mix thoroughly. Then add 0.8 g titanium dioxide and continue sonicating for 30 min to obtain a mixed solution. The sonication power is 300 W and the frequency is 55 kHz. Step 2: Pour the mixed solution into a polytetrafluoroethylene inner liner and react at a solvothermal reaction temperature of 200℃ for 18 h. After natural cooling, remove the mixture and let it stand for 2 h to separate into layers. Then, use a dropper to remove the supernatant. After removing the supernatant, wash and filter the solid-liquid mixture with anhydrous ethanol and deionized water, and then dry it in a drying oven at 60℃. The high refractive index barium titanate nanofiller used in the nanoimprinting process is denoted as BaTiO3-5a. Compared to Example 3, this example uses a mixed solution of ethylene glycol and anhydrous ethanol as a solvent; the barium titanate nanofiller prepared in this example has a particle size of 27.6 nm and contains a small amount of unreacted TiO2 impurities.

[0033] Example 8 A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes includes the following steps: Step 1: Weigh 3.155g Ba(OH)2·8H2O into a mixed solution of 16 mL ethylene glycol methyl ether and 24 mL ethylene glycol, and sonicate for 30 min to mix thoroughly. Then add 0.8 g titanium dioxide and continue sonicating for 30 min to obtain a mixed solution. The sonication power is 300 W and the frequency is 55 kHz. Step 2: Pour the mixed solution into a polytetrafluoroethylene liner and react at a solvothermal reaction temperature of 200℃ for 18 h. After natural cooling, remove the solution and let it stand for 2 h to separate into layers. Then, use a dropper to remove the supernatant. After removing the supernatant, wash and filter the solid-liquid mixture with anhydrous ethanol and deionized water, and then dry it in a drying oven at 60℃. The high refractive index barium titanate nanofiller used in the nanoimprinting process is denoted as BaTiO3-6a. Compared to Example 3, this example uses a mixed solution of ethylene glycol methyl ether and ethylene glycol as a solvent; the barium titanate nanofiller prepared in this example has a particle size of 28.2 nm and contains a small amount of unreacted TiO2 impurities.

[0034] Example 9 A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes includes the following steps: Step 1: Weigh 3.155g Ba(OH)2·8H2O into a mixture of 10 mL ethylene glycol methyl ether, 22 mL anhydrous ethanol, and 8 mL ethylene glycol. Sonicate for 30 min to mix thoroughly. Then add 0.8 g titanium dioxide and continue sonicating for 30 min to obtain a mixed solution. The sonication power is 300 W and the frequency is 55 kHz. Step 2: Pour the mixed solution into a polytetrafluoroethylene inner liner and react at a solvothermal reaction temperature of 200℃ for 18 h. After natural cooling, remove the mixture and let it stand for 2 h to separate into layers. Then, use a dropper to remove the supernatant. After removing the supernatant, wash and filter the solid-liquid mixture with anhydrous ethanol and deionized water, and then dry it in a drying oven at 60℃. The high refractive index barium titanate nanofiller used in the nanoimprinting process is denoted as BaTiO3-7a. Compared to Example 3, this example uses a mixed solution of ethylene glycol methyl ether, anhydrous ethanol, and ethylene glycol as a solvent; the barium titanate nanofiller prepared in this example is free of impurities, has good crystallinity, and the corresponding crystal form is a cubic phase (PDF#01-075-0213) perovskite structure, with a narrow particle size distribution and a particle size of 22.7 nm.

[0035] Example 10 A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes includes the following steps: Step 1: Weigh 3.155g Ba(OH)2·8H2O into a mixture of 10 mL ethylene glycol methyl ether, 22 mL anhydrous ethanol, and 8 mL ethylene glycol. Sonicate for 30 min to mix thoroughly. Then add 0.8 g titanium dioxide and continue sonicating for 30 min to obtain a mixed solution. The sonication power is 300 W and the frequency is 55 kHz. Step 2: The mixed solution is subjected to a high-voltage pulsed electric field for 5 min, then poured into a polytetrafluoroethylene liner. The reaction is carried out at a solvothermal temperature of 200℃ for 18 h. After natural cooling, it is removed and allowed to stand while being subjected to a high-voltage pulsed electric field for 10 min. Then it is allowed to stand for another 0.5 h to separate into layers. The supernatant is then removed with a dropper. The solid-liquid mixture after removing the supernatant is washed and filtered with anhydrous ethanol and deionized water, and then dried in a drying oven at 60℃. The high-refractive-index barium titanate nanofiller used in the nanoimprinting process is designated as BaTiO3-8a. The electric field strength of the high-voltage pulsed electric field is 20 kV / cm, and the frequency is 300 Hz. Compared to Example 9, this example uses a high-voltage pulsed electric field to treat the solution; the barium titanate nanofiller prepared in this example is free of impurities, has good crystallinity, and the corresponding crystal form is a cubic phase (PDF#01-075-0213) perovskite structure, with a narrow particle size distribution and a particle size of 18.4 nm.

[0036] Example 11 A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes includes the following steps: Step 1: Weigh 3.155g Ba(OH)2·8H2O into a mixture of 10 mL ethylene glycol methyl ether, 22 mL anhydrous ethanol, and 8 mL ethylene glycol. Sonicate for 30 min to mix thoroughly. Then add 0.8 g titanium dioxide and continue sonicating for 30 min to obtain a mixed solution. The sonication power is 300 W and the frequency is 55 kHz. Step 2: The mixed solution is subjected to a high-voltage pulsed electric field for 5 min, then poured into a polytetrafluoroethylene liner. The reaction is carried out at a solvothermal temperature of 200℃ for 8 h. After natural cooling, it is removed and allowed to stand while being subjected to a high-voltage pulsed electric field for 10 min. Then it is allowed to stand for another 0.5 h to separate into layers. The supernatant is then removed with a dropper. The solid-liquid mixture after removing the supernatant is washed and filtered with anhydrous ethanol and deionized water, and then dried in a drying oven at 60℃. The high-refractive-index barium titanate nanofiller used in the nanoimprinting process is designated as BaTiO3-9a. The electric field strength of the high-voltage pulsed electric field is 20 kV / cm, and the frequency is 300 Hz. Compared to Example 10, this example shortens the solvothermal reaction time; the barium titanate nanofiller prepared in this example is free of impurities, has good crystallinity, and the corresponding crystal form is a cubic phase (PDF#01-075-0213) perovskite structure, with a narrow particle size distribution and a particle size of 20.2 nm.

[0037] In Examples 9-11, a specific composite solvent system (ethylene glycol methyl ether, anhydrous ethanol, and ethylene glycol) was selected. Experiments showed that the three solvents had a synergistic effect, which facilitated the dissolution and contact of the raw materials, promoted the reaction, and resulted in barium titanate with higher purity and narrower particle size distribution. In addition, in Examples 10-11, high-voltage pulsed electric field treatment enhanced the reactivity of the mixed solution and improved the efficiency of subsequent reactions. It also promoted crystal nucleation, regulated crystal growth, and facilitated solution stratification, which helped separate soluble impurities from the crystals. As a result, high-purity, uniformly sized, fine-particle-size, and stable cubic perovskite-structured barium titanate could be obtained in a shorter time.

[0038] In summary, this invention uses a solvothermal method to prepare barium titanate, using barium hydroxide and titanium dioxide as raw materials. By adjusting the raw material ratio, optimizing the solvent system, and combining it with a high-voltage pulsed electric field, high-purity, near-spherical barium titanate nanofillers with a particle size of <30nm were prepared, which can meet the requirements of nanoimprinting process.

[0039] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing high-refractive-index barium titanate nanofillers for nanoimprinting processes, characterized in that, Includes the following steps: Step 1: Add barium hydroxide octahydrate to the solvent and sonicate until homogeneous. Then add titanium dioxide and continue sonicating to obtain a mixed solution. Step 2: Transfer the mixed solution into the reactor for solvothermal reaction. After natural cooling, remove the solution and allow it to stand and separate into layers. Remove the supernatant, wash and filter the remaining solid-liquid mixture, and then dry it to obtain high refractive index barium titanate nanofiller for nanoimprinting process.

2. The method for preparing high-refractive-index barium titanate nanofiller for nanoimprinting as described in claim 1, characterized in that, In step one, the molar ratio of barium hydroxide octahydrate to titanium dioxide is 0.9~1.2:

1.

3. The method for preparing high-refractive-index barium titanate nanofiller for nanoimprinting as described in claim 1, characterized in that, In step one, the solvent is one or more of ethylene glycol methyl ether, anhydrous ethanol, and ethylene glycol.

4. The method for preparing high-refractive-index barium titanate nanofiller for nanoimprinting as described in claim 1, characterized in that, In step one, the mass-to-volume ratio of barium hydroxide octahydrate to solvent is 2-4 g: 30-50 mL.

5. The method for preparing high-refractive-index barium titanate nanofiller for nanoimprinting as described in claim 1, characterized in that, In step one, the ultrasonic power is 200~500W, the frequency is 40~70kHz, the ultrasonic mixing time is 10~60min, and the ultrasonic treatment continues for 10~60min.

6. The method for preparing high-refractive-index barium titanate nanofiller for nanoimprinting as described in claim 1, characterized in that, In step two, the solvothermal reaction temperature is 150~250℃, and the reaction time is 6~20h.

7. The method for preparing high-refractive-index barium titanate nanofiller for nanoimprinting as described in claim 1, characterized in that, In step two, the plant is left to stand for 0.5 to 3 hours; the drying temperature is 50 to 70°C.

8. The method for preparing high-refractive-index barium titanate nanofiller for nanoimprinting as described in claim 1, characterized in that, Step two is replaced by: subjecting the mixed solution to a high-voltage pulsed electric field treatment, then transferring it to a reactor for a solvothermal reaction, allowing it to cool naturally, removing it and allowing it to stand while simultaneously applying a high-voltage pulsed electric field treatment, then allowing it to stand and separate into layers, removing the supernatant, and washing, filtering, and drying the remaining solid-liquid mixture to obtain a high-refractive-index barium titanate nanofiller for nanoimprinting.

9. The method for preparing high-refractive-index barium titanate nanofiller for nanoimprinting as described in claim 8, characterized in that, The electric field strength of the high-voltage pulse electric field is 10~50 kV / cm, the frequency is 100~500 Hz, and the processing time is 3~15 min.

10. The application of a high-refractive-index barium titanate nanofiller prepared by the preparation method according to any one of claims 1-9 in nanoimprinting process.

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