BaTiO3 nanowire with high length-diameter ratio and template conversion preparation method thereof
By preparing TiO2 nanowire templates through the molten salt method and converting them into rod-shaped BaTiO3, the problems of insufficient template stability and crystal phase control in the existing technology are solved. This enables the large-scale preparation and morphology inheritance of high aspect ratio BaTiO3 nanowires, which are suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2026-02-11
- Publication Date
- 2026-05-15
AI Technical Summary
Existing technologies make it difficult to achieve large-scale preparation of BaTiO3 nanowires with high aspect ratio under low liquid or solid conditions, and the template stability and crystal phase control are insufficient, affecting morphology inheritance and impurity phase generation.
TiO2 nanowire templates were prepared by molten salt method. By controlling the amount of molten salt, calcination and conversion temperature, mixing ratio and salt washing treatment steps, the template morphology was preserved to the greatest extent during the conversion process, and rod-shaped BaTiO3 was prepared, which is suitable for industrialization.
The large-scale preparation of high aspect ratio BaTiO3 nanowires was achieved, ensuring template integrity and crystal phase control, reducing environmental and economic costs, and making them suitable for industrial applications.
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Figure CN122035937A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of inorganic functional ceramic materials and their preparation technology, and particularly relates to a high aspect ratio BaTiO3 nanowire and its template conversion preparation method. Background Technology
[0002] Barium titanate (BaTiO3) is a typical perovskite-structured functional ceramic material. Due to its excellent dielectric properties, piezoelectric properties, and thermal stability, it has wide applications in dielectric energy storage devices, piezoelectric sensors, and microelectronic devices. In recent years, with the development of devices towards higher energy density and miniaturization, one-dimensional BaTiO3 nanowires with high aspect ratios have shown significant advantages in polarization behavior, electrostrain, and microstructure control.
[0003] Existing methods for preparing BaTiO3 nanomaterials mainly include hydrothermal methods, sol-gel methods, solid-state sintering methods, and direct molten salt methods. Hydrothermal methods can prepare high-purity nanowires, but the reaction conditions are stringent, and the morphology consistency of the products is limited. Sol-gel and solid-state sintering methods are prone to generating impurity phases, and precise grain control is difficult. While the direct molten salt method has advantages in mass transfer rate and crystal growth control, it still has certain limitations in template selection, morphology preservation, and large-scale preparation.
[0004] The molten salt method possesses high ion mobility and low interfacial energy, which can promote the preferential growth of TiO2 nanostructures along specific crystal orientations, providing a morphological basis for subsequent template conversion. Currently, most publicly disclosed molten salt preparation techniques focus on using a two-step molten salt process to synthesize high aspect ratio BaTiO3 nanowires. The first step involves generating a one-dimensional BaTi2O5 nanowire template using molten salt, followed by a further molten salt reaction to prepare BaTiO3 nanowires, resulting in one-dimensional BaTiO3 nanomaterials (CN104925856A). However, this template has limited stability, insufficient control over grain orientation and impurity phases, and is difficult to recycle.
[0005] Although existing technologies can prepare one-dimensional BaTiO3 nanowires, a systematic method for using recyclable TiO2 nanowire templates and achieving morphology inheritance transformation under independent solid-phase or low-liquid-phase conditions has not yet been disclosed. The integrity of the template, the crystal phase, and the interfacial reaction conditions have a significant impact on the final nanowire morphology, grain size, and impurity phase formation. Furthermore, there remains a technological gap in the large-scale, controllable preparation of high aspect ratio BaTiO3 nanowires.
[0006] During the template conversion process, Ba 2+An in-situ BaTiO3 epitaxial layer is formed by diffusion on the TiO2 surface and grows along the template axis, achieving morphological inheritance. Template integrity and grain control are key technical factors for preparing high aspect ratio, one-dimensional oriented BaTiO3 nanowires. Therefore, developing a method for the large-scale preparation of high aspect ratio BaTiO3 nanowires under low liquid or solid phase conditions using a recyclable TiO2 nanowire template is of great significance. Summary of the Invention
[0007] To address the problems existing in the prior art, this invention provides a complete process for preparing TiO2 nanowire templates using the molten salt method and preparing rod-shaped BaTiO3 based on the templates. The process clearly defines the amount of molten salt, the calcination and conversion temperature program, the mixing ratio, the salt washing and post-treatment steps, ensuring that the template morphology is preserved to the maximum extent during the conversion process and is converted into rod-shaped BaTiO3. The process is also suitable for industrialization.
[0008] To achieve the above objectives, in a first aspect, the present invention provides a template conversion preparation method for high aspect ratio BaTiO3 nanowires, comprising the following steps: Weigh out the raw materials NaH2PO4, NaCl, and TiO2 according to the mass ratio NaH2PO4:NaCl:TiO2=1:3:1; The raw material was subjected to bidirectional ball milling and dried to obtain precursor powder; The precursor powder and molten salt are mixed evenly according to the set amount, and the temperature is raised from room temperature to 700~900℃ at 5℃ / min and held for 300~360min. Then the temperature is lowered to 50℃ in the furnace to obtain the product. The obtained product was washed with salt and then centrifuged or allowed to settle to collect the TiO2 nanowire template. The collected TiO2 nanowire template was then dried. The obtained TiO2 nanowire template was mixed with a barium source and subjected to heat treatment conversion to generate a product containing barium titanate. The barium source was BaCl2 and BaCO3. The heat treatment conditions were: heating from room temperature to 980~1000℃ at 5℃ / min and holding for 60~70min, and then cooling to room temperature in the furnace. The soluble residues in the product containing barium titanate were washed away and dried to obtain rod-shaped BaTiO3.
[0009] Furthermore, the molten salts used are NaCl and Na2HPO4, and the amount of molten salt used is 4 times the total mass of the raw materials.
[0010] Further, the salt washing treatment of the obtained product includes: repeatedly rinsing with boiling deionized water and ultrasonic cleaning to dissolve and remove the molten salt auxiliary agent until the washing liquid is visually free of white precipitate; recovering the washing brine, ultrasonically dispersing and centrifuging to obtain molten salt and recovering it.
[0011] Furthermore, the barium source is a combination of BaCl2 and BaCO3; the mass ratio of TiO2 nanowire template to BaCl2 is 1:8, and the molar ratio of TiO2 nanowire template to BaCO3 is 1:0.5; during heat treatment, the reactants are covered or an inert gas is added to the reaction atmosphere.
[0012] Furthermore, 0.1 wt% NaCl is added during heat treatment.
[0013] Furthermore, after washing away the soluble residues in the product containing barium titanate and drying, it is annealed at 700-850℃ for 1.5-2 hours.
[0014] Furthermore, the solution is repeatedly washed with hot deionized water and sonicated. The washing solution is then centrifuged or allowed to settle, the supernatant is discarded, and the precipitate is collected as barium titanate.
[0015] Furthermore, the TiO2 nanowire template was mixed with the barium source and then subjected to low-speed roller milling at a speed of 120 rpm / min.
[0016] Secondly, the present invention provides a rod-shaped barium titanate, which is prepared by template conversion using the above-mentioned high aspect ratio BaTiO3 nanowire preparation method. The length of the rod-shaped BaTiO3 is 0.5-20 μm and the diameter is 30-600 nm.
[0017] Thirdly, the present invention provides a method for applying the barium titanate rods as described above, wherein the obtained barium titanate rods are treated with surfactants and then used for interfacial self-assembly or composited with polymers to prepare anisotropic composite materials. Alternatively, the obtained rod-shaped BaTiO3 can be pressed into ceramic sheets and sintered to prepare piezoelectric or dielectric devices.
[0018] Compared with existing technologies, this invention has at least the following advantages: This invention uses a molten salt method to prepare TiO2 nanowire templates, utilizing the liquid phase migration and melt-recrystallization properties of molten salt to promote the formation of TiO2 nanowires / linear templates and increase template yield. Subsequently, in the template-barium source conversion step, a barium source is added, allowing the template to gradually transform into perovskite-structured BaTiO3 while maintaining its rod-like morphology, thereby ensuring high morphology fidelity and good crystallinity of the product. This method is simple to operate, repeatable, suitable for scale-up, and reduces environmental and economic costs through molten salt recycling.
[0019] This invention emphasizes molten salt recovery and recycling in scale-up manufacturing to reduce material costs and wastewater / waste salt pollution; it recommends the use of a multi-washing and crystallization recovery system, and includes molten salt circulation, recovery efficiency and quality control methods in the process documentation. Attached Figure Description
[0020] Figure 1This is a schematic diagram of the overall preparation process of the present invention.
[0021] Figure 2 The image shown is a SEM image of the TiO2 nanowire template in the example.
[0022] Figure 3 The image shown is a SEM image of the rod-shaped BaTiO3 obtained in the example.
[0023] Figure 4 The image shown is the XRD pattern of the sample obtained in the example. Detailed Implementation
[0024] The present invention will be described in detail below with reference to several embodiments, but the present invention is not limited to these embodiments. The parameters given below are preferred ranges or example values, and can be adjusted accordingly based on the scale of the process and equipment conditions in actual applications.
[0025] The flowchart of the preparation method described in this invention is shown below. Figure 1 .
[0026] Example 1 Step 1: Prepare TiO2 nanowire templates.
[0027] S11, Ingredients: Weigh NaH2PO4, NaCl, and TiO2 according to the mass ratio NaH2PO4:NaCl:TiO2=1:3:1, add ethanol as a dispersant, and transfer to a zirconia ball mill jar. NaH2PO4 is used as a morphology guiding agent to promote the formation of linear structures.
[0028] S12, Ball milling: Bidirectional ball milling was performed using zirconia grinding balls at a frequency of approximately 20 Hz, for 60 min × 3 times, with a 2 min interval, for a total of approximately 6 hours. The purpose of ball milling was to ensure uniform dispersion of the excipients and reduce the agglomeration of the template precursor powder.
[0029] S13, Drying: The ball-milled product is dried in an oven at 70°C to obtain precursor powder.
[0030] S14, Molten Salt Calcination (Template Formation): The precursor powder is loaded into a refractory crucible and covered; it is then placed in a muffle furnace. Example heating program: The temperature is increased from room temperature to 700°C at a rate of 5°C / min and held for 360 min, then cooled to 50°C with the furnace to obtain the product. In the molten salt medium, the high temperature melts the salt and provides channels for liquid phase migration, promoting the recrystallization and linear growth of TiO2.
[0031] S15, Salt washing and template recovery: The product is repeatedly rinsed with boiling deionized water and treated with molten salt and TiO2 in an ultrasonic bath for 10 min to dissolve and remove the molten salt auxiliary agent; silver nitrate is used to detect whether the washing solution contains residual chloride ions until there is no obvious white precipitate; the TiO2 nanowire template is collected by centrifugation or static sedimentation and dried at 70℃ for later use; the washing brine is recovered and concentrated and crystallized to recycle the molten salt.
[0032] Template characterization: Scanning electron microscopy (SEM) revealed that the TiO2 product exhibited a linear / rod-like structure; XRD confirmed the TiO2 phase as either anatase or rutile; BET was used to measure the specific surface area and record the template morphology parameters; the TiO2 template crystal phase was anatase or rutile, which was obtained by selectively adsorbing anions from the salt onto certain high surface energy crystal faces of TiO2, inhibiting its lateral growth, and allowing the crystal to preferentially grow along the longitudinal direction to obtain the desired phase.
[0033] Step 2: The template is mixed with the barium source and then converted.
[0034] S21, Take the TiO2 nanowire template recovered and dried in Example 1 and mix it with BaCl2 at a mass ratio of TiO2:BaCl2=1:8. The molar ratio of TiO2 nanowire template to BaCO3 is 1:0.5. Mix it evenly. 0.1wt% NaCl flux can be added as needed to improve the mixing uniformity.
[0035] S22, TiO2 nanowire templates are mixed with BaCl2 and BaCO3 at low speed to avoid template breakage. They can be rolled at low speed using a roller mill, with the speed set at 120 rpm / min, to ensure the morphology of the template is preserved.
[0036] S23, load the mixture into a refractory crucible and cover the crucible; to reduce volatilization loss, place a lid on top of the crucible or heat it under an inert atmosphere.
[0037] S24 Place the crucible into the furnace. Example procedure: Heat from room temperature to 980°C at a rate of 5°C / min and hold for 60 minutes, then cool down to room temperature with the furnace. Within this temperature range, Ba... 2+ It can react with the TiO2 template interface to generate the BaTiO3 phase, forming a perovskite coating along the template axis and completing the phase transformation, thereby obtaining rod-shaped BaTiO3.
[0038] S25, after the reaction is cooled, wash repeatedly with hot deionized water and sonicate for 10 min. Centrifuge or let the washing solution settle, discard the supernatant, collect the precipitate and dry it at 70℃.
[0039] As an optimized process, short-time annealing at 700℃ for 2 hours on dried rod-shaped BaTiO3 can improve its crystallinity.
[0040] Example 2 Step 1: Prepare TiO2 nanowire templates.
[0041] S11, Ingredients: Take NaH2PO4, NaCl, and TiO2 in a mass ratio of NaH2PO4:NaCl:TiO2=1:3:1, and use an appropriate amount of anhydrous ethanol as a dispersant. Transfer them to a zirconia ball mill jar. NaH2PO4 is used as a morphology guiding agent to promote the formation of linear structures.
[0042] S12, Ball milling: Bidirectional ball milling was performed using zirconia grinding balls at a frequency of 20 Hz, 60 min × 3 times, with 2 min intervals, for a total of approximately 6 hours. The purpose of ball milling was to ensure uniform dispersion of the excipients and reduce the agglomeration of the template precursor powder.
[0043] S13, Drying: The ball-milled product is dried in an oven at 70°C to obtain precursor powder.
[0044] S14, Molten Salt Calcination (Template Formation): The precursor powder is loaded into a refractory crucible and covered with a crucible lid; it is then placed in a muffle furnace and heated from room temperature to 800℃ at a rate of 5℃ / min, held for 340 min, and then cooled to 50℃ with the furnace to obtain the product. In the molten salt medium, the high temperature melts the salt and provides channels for liquid phase migration, promoting the recrystallization and linear growth of TiO2.
[0045] S15, Salt washing and template recovery: The product is repeatedly rinsed with boiling deionized water and sonicated for 15 minutes to remove molten salt impurities coated on the product surface, while dispersing TiO2 particles to prevent agglomeration and maintain their complete one-dimensional morphology; silver nitrate is used to detect whether the washing solution contains residual chloride ions until no obvious white precipitate is found; the TiO2 nanowire template is collected by centrifugation or static sedimentation and dried at 70°C for later use; the washing brine is recovered, concentrated and crystallized to recycle the molten salt.
[0046] Step 2: The template is mixed with the barium source and then converted.
[0047] S21. Take the recovered and dried TiO2 nanowire template and BaCl2 at a mass ratio of TiO2:BaCl2=1:8 and a molar ratio of TiO2 nanowire template to BaCO3 of 1:0.5. Mix them evenly and add 0.1wt% NaCl to improve the mixing. S22, TiO2 nanowire templates are mixed with BaCl2 at low speed to avoid template breakage. They can be rolled at low speed using a roller mill with a rotation speed of 120 rpm / min to ensure the morphology of the template is preserved. S23, Load the mixture into a refractory crucible and cover it with the crucible lid; S24, place the crucible in the furnace, raise the temperature from room temperature to 990℃ at a rate of 5℃ / min and hold for 70 min, then cool the furnace to room temperature; within this temperature range, Ba2+ It can react with the TiO2 template interface to generate the BaTiO3 phase, forming a perovskite coating along the template axis and completing the phase transformation, thereby obtaining rod-shaped BaTiO3.
[0048] S25, after the reaction is cooled, wash repeatedly with hot deionized water and sonicate for 30 min. Centrifuge or let the washing solution settle, discard the supernatant, collect the precipitate and dry it at 70℃. Anneal the dried rod-shaped BaTiO3 at 700℃ for 2 h to improve the crystallinity.
[0049] Example 3 Step 1: Prepare TiO2 nanowire templates.
[0050] S11, Ingredients: Take NaH2PO4, NaCl, and TiO2 in a mass ratio of NaH2PO4:NaCl:TiO2=1:3:1, and use an appropriate amount of anhydrous ethanol as a dispersant. Transfer them to a zirconia ball mill jar. NaH2PO4 is used as a morphology guiding agent to promote the formation of linear structures.
[0051] S12, Ball milling: Bidirectional ball milling was performed using zirconia grinding balls at a frequency of 20 Hz, 60 min × 3 times, with 2 min intervals, for a total of approximately 6 hours. The purpose of ball milling was to ensure uniform dispersion of the excipients and reduce the agglomeration of the template precursor powder.
[0052] S13, Drying: The ball-milled product is dried in an oven at 70°C to obtain precursor powder.
[0053] S14, Molten Salt Calcination (Template Formation): The precursor powder is loaded into a refractory crucible and covered with a crucible lid; it is then placed in a muffle furnace and heated from room temperature to 850°C at a rate of 5°C / min, held for 360 min, and then cooled to 50°C with the furnace to obtain the product. In the molten salt medium, the high temperature melts the salt and provides channels for liquid phase migration, promoting the recrystallization and linear growth of TiO2.
[0054] S15, Salt washing and template recovery: The product is repeatedly rinsed with boiling deionized water and sonicated for 20 minutes to remove molten salt impurities coated on the product surface, while dispersing TiO2 particles to prevent agglomeration and maintain their complete one-dimensional morphology; silver nitrate is used to detect whether the washing solution contains residual chloride ions until no obvious white precipitate is found; the TiO2 nanowire template is collected by centrifugation or static sedimentation and dried at 70°C for later use; the washing brine is recovered, concentrated and crystallized to recycle the molten salt.
[0055] Step 2: The template is mixed with the barium source and then converted.
[0056] S21. Take the recovered and dried TiO2 nanowire template and BaCl2 at a mass ratio of TiO2:BaCl2=1:8 and a molar ratio of TiO2 nanowire template to BaCO3 of 1:0.5. Mix them evenly and add 0.1wt% NaCl to improve the mixing. S22, TiO2 nanowire templates are mixed with BaCl2 at low speed to avoid template breakage. They can be rolled at low speed using a roller mill with a rotation speed of 120 rpm / min to ensure the morphology of the template is preserved. S23, Load the mixture into a refractory crucible and cover it with the crucible lid; S24, Place the crucible into the furnace. Example procedure: Increase the temperature from room temperature to 990℃ at a rate of 5℃ / min and hold for 65 min, then cool the furnace to room temperature. Within this temperature range, Ba... 2+ It can react with the TiO2 template interface to generate the BaTiO3 phase, forming a perovskite coating along the template axis and completing the phase transformation, thereby obtaining rod-shaped BaTiO3.
[0057] S25, after the reaction is cooled, wash repeatedly with hot deionized water and sonicate for 30 min. Centrifuge or let the washing solution settle, discard the supernatant, collect the precipitate and dry it at 70℃. Anneal the dried rod-shaped BaTiO3 at 700℃ for 2 h to improve the crystallinity.
[0058] Example 4 Step 1: Prepare TiO2 nanowire templates.
[0059] S11, Ingredients: Take NaH2PO4, NaCl, and TiO2 in a mass ratio of NaH2PO4:NaCl:TiO2=1:3:1, and use an appropriate amount of anhydrous ethanol as a dispersant. Transfer them to a zirconia ball mill jar. NaH2PO4 is used as a morphology guiding agent to promote the formation of linear structures.
[0060] S12, Ball milling: Bidirectional ball milling was performed using zirconia grinding balls at a frequency of 20 Hz, 60 min × 3 times, with 2 min intervals, for a total of approximately 6 hours. The purpose of ball milling was to ensure uniform dispersion of the excipients and reduce the agglomeration of the template precursor powder.
[0061] S13, Drying: The ball-milled product is dried in an oven at 70°C to obtain precursor powder.
[0062] S14, Molten Salt Calcination (Template Formation): The precursor powder is loaded into a refractory crucible and covered with a crucible lid; it is then placed in a muffle furnace and heated from room temperature to 900℃ at a rate of 5℃ / min, held for 300 min, and then cooled to 50℃ with the furnace to obtain the product. In the molten salt medium, the high temperature melts the salt and provides a channel for liquid phase migration, promoting the recrystallization and linear growth of TiO2.
[0063] S15, Salt washing and template recovery: The product is repeatedly rinsed with boiling deionized water and sonicated for 20 minutes to remove molten salt impurities coated on the product surface, while dispersing TiO2 particles to prevent agglomeration and maintain their complete one-dimensional morphology; silver nitrate is used to detect whether the washing solution contains residual chloride ions until no obvious white precipitate is found; the TiO2 nanowire template is collected by centrifugation or static sedimentation and dried at 70°C for later use; the washing brine is recovered, concentrated and crystallized to recycle the molten salt.
[0064] Step 2: The template is mixed with the barium source and then converted.
[0065] S21. Take the recovered and dried TiO2 nanowire template and BaCl2 at a mass ratio of TiO2:BaCl2=1:8 and a molar ratio of TiO2 nanowire template to BaCO3 of 1:0.5. Mix them evenly and add 0.1wt% NaCl to improve the mixing. S22, TiO2 nanowire templates are mixed with BaCl2 at low speed to avoid template breakage. They can be rolled at low speed using a roller mill with a rotation speed of 120 rpm / min to ensure the morphology of the template is preserved. S23, Load the mixture into a refractory crucible and cover it with the crucible lid; S24, place the crucible in the furnace, raise the temperature from room temperature to 990℃ at a rate of 5℃ / min and hold for 65min, then cool it down to room temperature with the furnace; within this temperature range, Ba 2+ It can react with the TiO2 template interface to generate the BaTiO3 phase, forming a perovskite coating along the template axis and completing the phase transformation, thereby obtaining rod-shaped BaTiO3.
[0066] S25, after the reaction is cooled, wash repeatedly with hot deionized water and sonicate for 30 min. Centrifuge or let the washing solution settle, discard the supernatant, collect the precipitate and dry it at 70℃. Anneal the dried rod-shaped BaTiO3 at 800℃ for 1.5 h to improve the crystallinity.
[0067] Example 5 Step 1: Prepare TiO2 nanowire templates.
[0068] S11, Ingredients: Take NaH2PO4, NaCl, and TiO2 in a mass ratio of NaH2PO4:NaCl:TiO2=1:3:1, and use an appropriate amount of anhydrous ethanol as a dispersant. Transfer them to a zirconia ball mill jar. NaH2PO4 is used as a morphology guiding agent to promote the formation of linear structures.
[0069] S12, Ball milling: Bidirectional ball milling was performed using zirconia grinding balls at a frequency of 20 Hz, 60 min × 3 times, with 2 min intervals, for a total of approximately 6 hours. The purpose of ball milling was to ensure uniform dispersion of the excipients and reduce the agglomeration of the template precursor powder.
[0070] S13, Drying: The ball-milled product is dried in an oven at 70°C to obtain precursor powder.
[0071] S14, Molten Salt Calcination (Template Formation): The precursor powder is loaded into a refractory crucible and covered with a crucible lid; it is then placed in a muffle furnace and heated from room temperature to 900℃ at a rate of 5℃ / min, held for 300 min, and then cooled to 50℃ with the furnace to obtain the product. In the molten salt medium, the high temperature melts the salt and provides a channel for liquid phase migration, promoting the recrystallization and linear growth of TiO2.
[0072] S15, Salt washing and template recovery: The product is repeatedly rinsed with boiling deionized water and sonicated for 20 minutes to remove molten salt impurities coated on the product surface, while dispersing TiO2 particles to prevent agglomeration and maintain their complete one-dimensional morphology; silver nitrate is used to detect whether the washing solution contains residual chloride ions until no obvious white precipitate is found; the TiO2 nanowire template is collected by centrifugation or static sedimentation and dried at 70°C for later use; the washing brine is recovered, concentrated and crystallized to recycle the molten salt.
[0073] Step 2: The template is mixed with the barium source and then converted.
[0074] S21. Take the recovered and dried TiO2 nanowire template and BaCl2 at a mass ratio of TiO2:BaCl2=1:8 and a molar ratio of TiO2 nanowire template to BaCO3 of 1:0.5. Mix them evenly and add 0.1wt% NaCl to improve the mixing. S22, TiO2 nanowire templates are mixed with BaCl2 at low speed to avoid template breakage. They can be rolled at low speed using a roller mill with a rotation speed of 120 rpm / min to ensure the morphology of the template is preserved. S23, Load the mixture into a refractory crucible and cover it with the crucible lid; S24, Place the crucible into the furnace. Example procedure: Increase the temperature from room temperature to 1000℃ at 5℃ / min and hold for 60min, then cool the furnace back to room temperature. Within this temperature range, Ba... 2+ It can react with the TiO2 template interface to generate the BaTiO3 phase, forming a perovskite coating along the template axis and completing the phase transformation, thereby obtaining rod-shaped BaTiO3.
[0075] S25, after the reaction is cooled, wash repeatedly with hot deionized water and sonicate for 30 min. Centrifuge or let the washing solution settle, discard the supernatant, collect the precipitate and dry it at 70℃. Anneal the dried rod-shaped BaTiO3 at 850℃ for 1 h to improve the crystallinity.
[0076] Example 6 In the scale-up process, it is recommended to use a continuous recovery system for molten salt, a muffle furnace for calcination to ensure uniform temperature, and a continuous low-speed roller mill for mixing to reduce template breakage.
[0077] Figure 2 This is a SEM image of the rod-shaped TiO2 nanowire template obtained in this embodiment. The SEM shows that the product is in the shape of a regular rod, with a length of 1-10 μm and a diameter of 80-200 nm.
[0078] Figure 3 This is a SEM image of the rod-shaped BaTiO3 obtained in this embodiment. The SEM shows that the product is in the shape of a regular rod, with a length of 1-20 μm and a diameter of 240-600 nm.
[0079] Figure 4 The XRD pattern of the rod-shaped barium titanate obtained in this embodiment is shown. During XRD detection, 2θ = 22.1° (100), 31.5° (110), 38.8° (111), 45.2° (200), and 50.9° (210), which conforms to the BaTiO3 perovskite phase.
[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing high aspect ratio BaTiO3 nanowires by template conversion, characterized in that, Includes the following steps: Weigh out the raw materials NaH2PO4, NaCl, and TiO2 according to the mass ratio NaH2PO4:NaCl:TiO2=1:3:1; The raw material was subjected to bidirectional ball milling and dried to obtain precursor powder; The precursor powder and molten salt are mixed evenly according to the set amount, and the temperature is raised from room temperature to 700~900℃ at 5℃ / min and held for 300~360min. Then the temperature is lowered to 50℃ in the furnace to obtain the product. The obtained product was washed with salt and then centrifuged or allowed to settle to collect the TiO2 nanowire template. The collected TiO2 nanowire template was then dried. The obtained TiO2 nanowire template was mixed with a barium source and subjected to heat treatment conversion to generate a product containing barium titanate. The barium source was BaCl2 and BaCO3. The heat treatment conditions were: heating from room temperature to 980~1000℃ at 5℃ / min and holding for 60~70min, and then cooling to room temperature in the furnace. The soluble residues in the product containing barium titanate were washed away and dried to obtain rod-shaped BaTiO3.
2. The template conversion preparation method for high aspect ratio BaTiO3 nanowires according to claim 1, characterized in that, The molten salts used are NaCl and Na2HPO4, and the amount of molten salt used is 4 times the total mass of the raw materials.
3. The template conversion preparation method for high aspect ratio BaTiO3 nanowires according to claim 1, characterized in that, The washing treatment of the obtained product includes: repeatedly rinsing with boiling deionized water and ultrasonic cleaning to dissolve and remove the molten salt auxiliary agent until the washing liquid is visually free of white precipitate; recovering the washing brine, ultrasonically dispersing and centrifuging to obtain molten salt and recovering it.
4. The template conversion preparation method for high aspect ratio BaTiO3 nanowires according to claim 1, characterized in that, The barium source is a combination of BaCl2 and BaCO3; the mass ratio of TiO2 nanowire template to BaCl2 is 1:8, and the molar ratio of TiO2 nanowire template to BaCO3 is 1:0.5; during heat treatment, the reactants are covered or an inert gas is added to the reaction atmosphere.
5. The template conversion preparation method for high aspect ratio BaTiO3 nanowires according to claim 1, characterized in that, 0.1 wt% NaCl was added during heat treatment.
6. The template conversion preparation method for high aspect ratio BaTiO3 nanowires according to claim 1, characterized in that, After washing away soluble residues from the product containing barium titanate and drying, anneal at 700-850℃ for 1-2 hours.
7. The template conversion preparation method for high aspect ratio BaTiO3 nanowires according to claim 1, characterized in that, The solution was repeatedly washed with hot deionized water and sonicated. The washing solution was then centrifuged or allowed to settle. The supernatant was discarded and the precipitate was collected as barium titanate.
8. The template conversion preparation method for high aspect ratio BaTiO3 nanowires according to claim 1, characterized in that, The TiO2 nanowire template was mixed with the barium source and then subjected to low-speed roller milling at a speed of 120 rpm / min.
9. A rod-shaped barium titanate, characterized in that, The high aspect ratio BaTiO3 nanowires were prepared by template conversion according to any one of claims 1-9. The length of the rod-shaped BaTiO3 nanowires was 0.5-20 μm and the diameter was 30-600 nm.
10. The method of applying the rod-shaped barium titanate as described in claim 9, characterized in that, The obtained rod-shaped BaTiO3 was treated with surfactants and then used for interfacial self-assembly or compounded with polymers to prepare anisotropic composite materials. Alternatively, the obtained rod-shaped BaTiO3 can be pressed into ceramic sheets and sintered to prepare piezoelectric or dielectric devices.