Preparation method of barium titanate powder with hickory-like surface and nanocrystals

Abstract

The application discloses a preparation method of hickory-shaped barium titanate powder with nanocrystals on the surface, and comprises the following steps: step one, adding a barium chloride dihydrate solution prepared by mixing barium chloride dihydrate, ethanol and water into a transparent PEG solution, continuously stirring at room temperature, and obtaining a uniform and clear barium-polymer integrated precursor solution; step two, adding tetrabutyl titanate into an ethanol solution, stirring and aging, and obtaining a light yellow titanium source solution; step three, slowly adding the light yellow titanium source solution into the barium-polymer integrated precursor solution under strong stirring, obtaining a milky white suspension, and separating the solid and liquid after standing; step four, slowly adding a reaction promoter into the solid-liquid separated suspension, and obtaining a hydrothermal reaction precursor solution; and step five, carrying out a staged hydrothermal reaction on the precursor solution, and obtaining the powder after separation, washing and drying. The application is simple in operation, is beneficial to large-scale production, and can be applied to the field of catalysis and the like.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials, specifically relating to a method for preparing pecan-shaped barium titanate powder with nanocrystals on its surface. Background Technology

[0002] Barium titanate, as an important ferroelectric / piezoelectric material, possesses excellent photocatalytic and piezoelectric catalytic properties, showing great potential for application in environmental remediation. However, traditional barium titanate catalysts often face bottlenecks such as limited specific surface area leading to insufficient active sites, and high recombination rate of photogenerated carriers limiting catalytic efficiency. Therefore, synthesizing fine-sized nano-barium titanate particles, with their larger specific surface area, can lay the foundation for exhibiting higher performance. For example, near-spherical barium titanate particles (CN107151029A) with a diameter of 60-150 nm and finely dispersed barium titanate particles (CN120664872A) with an average particle size between 80-150 nm have been synthesized via the sol-hydrothermal method. Furthermore, spherical, highly tetragonal barium titanate powders with an average particle size of approximately 80 nm (CN114477273A) and an average particle size of less than 200 nm (CN116639972A) have been synthesized via the hydrothermal method. However, while the fine particle size brings high specific surface area and high performance, it also inherently brings the pain point of difficult recycling. Therefore, the synthesized fine barium titanate is often limited to the field of dielectric ceramics industry, which seriously restricts its widespread application in the field of environmental remediation.

[0003] To fully realize the application potential of barium titanate in environmental remediation, obtaining stable and long-lasting barium titanate catalysts is a preferred approach. Among these, the synthesis of micro / nano-structured barium titanate powders has attracted widespread attention due to its advantages such as high specific surface area, abundant active sites, efficient charge separation capability, and good stability. For example, porous barium titanate microsheets (CN116924462A), third-order inherited dendritic micro / nano-structured barium titanate (CN114890461A), micro / nano-hierarchical barium titanate microspheres (CN106430295A), and porous barium titanate micro / nano-particle spheres (CN106315667A) have been synthesized, exhibiting excellent performance due to their micro / nano-structures. However, the intrinsic structure of the crystal often hinders the formation of micro / nano-structured products during crystal synthesis. Therefore, complex synthesis processes are often required to obtain micro / nano-structured products, such as additive manufacturing (CN104355290A), mold-assisted synthesis (CN118080029A), stepwise hydrothermal synthesis (CN106430295A), and hydrothermal followed by high-temperature calcination (CN106315667A). Therefore, developing a simple synthesis method to obtain barium titanate materials with high specific surface area, abundant active sites, efficient charge separation capability, and good stability is of great significance for promoting the development of piezoelectric-photocatalysis technology. Summary of the Invention

[0004] In order to overcome the problems of the prior art, the present invention provides a method for preparing pecan-shaped barium titanate powder with nanocrystals on the surface that is low in cost, simple in process, and suitable for mass production.

[0005] The technical solution of this invention is: a method for preparing pecan-shaped barium titanate powder with nanocrystals on its surface, characterized by comprising the following steps:

[0006] Step 1: Add the barium chloride dihydrate solution prepared by barium chloride dihydrate, ethanol, and water to the transparent PEG solution and stir continuously at room temperature to obtain a uniform and clear barium-polymer integration precursor solution.

[0007] Step 2: Tetrabutyl titanate is gradually added dropwise to the ethanol solution, and after stirring and aging, a pale yellow titanium source solution is obtained;

[0008] Step 3: Under vigorous stirring, the above pale yellow titanium source solution is slowly added dropwise to the barium-polymer integration precursor solution using a constant flow pump to obtain a milky white suspension, which is then separated into solid and liquid components after standing.

[0009] Step 4: Slowly add a reaction promoter to the above solid-liquid separation suspension to obtain a hydrothermal reaction precursor solution;

[0010] Step 5: The precursor solution is subjected to a fractional hydrothermal reaction. After the reaction, the product is separated, washed, and dried to obtain pecan-shaped barium titanate powder.

[0011] In step one, the mass of barium chloride dihydrate, ethanol, and water are 0.24–0.25 g, 5 g, and 40–45 g, respectively; the average molecular weight of the PEG solution is 40,000, and its mass is 1 g.

[0012] In step two, the concentration of the pale yellow titanium source solution is 1 mol / L, the volume is 9–11 ml, and the aging time is 30 min.

[0013] In step three, the stirring speed is 600 rpm and the constant flow pump drip rate is 0.5 ml / min. After solid-liquid separation, the upper layer is clear liquid and the lower layer is white precipitate.

[0014] In step four, the reaction promoter is a 9 mol / L NaOH solution, added in an amount of 10–15 g.

[0015] The heating regime for the staged hydrothermal reaction process in step five is as follows: first, the temperature is raised from room temperature to 160°C at a rate of 2°C / min, and held at this temperature for 2 hours; then, the temperature is raised to 200-220°C at a rate of 1°C / min, and held at this temperature for 20-28 hours.

[0016] The washing process in step five involves first washing with dilute hydrochloric acid and then washing with deionized water until neutral.

[0017] The drying process in step five involves drying at 80–90°C for 4–8 hours.

[0018] In step five, the hydrothermal reactor is filled to 70%.

[0019] In step five, the walnut-shaped barium titanate powder has a size of 1μm×2μm, with grooves inside the monomer and a surface rich in nanocrystals.

[0020] The present invention has the following beneficial effects:

[0021] This invention utilizes a PEG-alcohol-water homogeneous liquid as the reaction solvent, creating a confined space for crystal growth and inducing the formation of micro / nano structures, effectively avoiding the smooth structures resulting from classical crystal growth theory. Here, the network structure of the PEG-alcohol-water homogeneous liquid solvent effectively slows down the hydrolysis rate of the titanium source and the migration rate of ions, thus slowing down the formation rate of crystal nuclei and preventing contact, thereby achieving controllable nucleation to form uniform primary particles. Furthermore, during crystal growth, the surface-connected PEG-alcohol chains alter the crystal growth path, slowing down the dissolution and redeposition of fine crystals and resulting in incomplete crystal fusion and oriented adsorption behavior, thus exhibiting a confined ripening process and inducing the formation of irregular, grooved, pecan-shaped micron-sized substrates. Furthermore, the nascent barium titanate nuclei, after surface modification with PEG-alcohol chains, create confined regions for their growth, effectively hindering reactant migration and inhibiting their growth, thus exhibiting a "frozen" growth. This ultimately produces a large number of extremely small barium titanate crystal particles, which, when loaded onto the micron-scale substrate surface, form a pecan-shaped barium titanate with numerous nanocrystals on its surface. The barium titanate catalyst synthesized by this method exhibits a micron-scale pecan-shaped morphology with numerous nanocrystals on its surface, possessing micro / nanostructure characteristics, high purity, and excellent piezoelectric, photocatalytic, and piezoelectric-photocatalytic properties, demonstrating stable and long-lasting performance. This synthesis method is simple and convenient, effectively avoiding the complex processes and high costs associated with conventional micro / nanostructure material preparation. Attached Figure Description

[0022] Figure 1 This is a SEM image (×30kx) of the powder obtained in Embodiment 1 of the present invention.

[0023] Figure 2 This is a SEM image (×100k magnification) of the powder obtained in Embodiment 1 of the present invention.

[0024] Figure 3 This is the X-ray diffraction pattern of the powder obtained in Embodiment 1 of the present invention;

[0025] Figure 4 These are the surface TEM morphology and energy dispersive spectroscopy mapping images of the powder obtained in Embodiment 1 of this invention;

[0026] Figure 5 This is a graph showing the performance of the powder obtained in Example 1 of this invention in piezoelectric catalytic degradation of Congo red dye;

[0027] Figure 6 This is a graph showing the photocatalytic degradation performance of Congo red dye by the powder obtained in Example 1 of this invention;

[0028] Figure 7 This is a graph showing the performance of the powder obtained in Example 1 of this invention in piezoelectric-photocatalytic degradation of Congo red dye;

[0029] Figure 8 This is a cycle stability diagram of the piezoelectric-photocatalytic degradation of Congo red dye by the powder obtained in Example 1 of the present invention. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Example 1

[0031] A method for preparing pecan-shaped barium titanate powder with nanocrystals on its surface, characterized by comprising the following steps:

[0032] Step 1: Add the barium chloride dihydrate solution prepared by 0.24g barium chloride dihydrate, 5g ethanol and 40g water to a transparent 1g PEG40000 solution, and stir continuously at room temperature for 1h to obtain a uniform and clear barium-polymer integration precursor solution.

[0033] Step 2: Tetrabutyl titanate is gradually added dropwise to the ethanol solution. After stirring and aging for 30 minutes, a pale yellow titanium source solution with a volume of 10 ml and a concentration of 1 mol / L is obtained.

[0034] Step 3: Under vigorous stirring at 600 rpm, the above pale yellow titanium source solution was slowly added dropwise to the barium-polymer integration precursor solution at a rate of 0.5 ml / min using a constant flow pump to obtain a milky white suspension. After standing for 10 min, the solid and liquid were separated, with the upper layer being clear liquid and the lower layer being a white precipitate.

[0035] Step 4: Slowly add 15g of 9mol / L NaOH solution to the above solid-liquid separation suspension to obtain the hydrothermal reaction precursor solution;

[0036] Step 5: The precursor solution is loaded into a hydrothermal reactor for a staged hydrothermal reaction. After the reaction, the product is separated, washed, and dried to obtain pecan-shaped barium titanate powder.

[0037] The heating regime for the staged hydrothermal reaction process in step five is as follows: first, the temperature is raised from room temperature to 160°C at a rate of 2°C / min, and held at this temperature for 2 hours; then, the temperature is raised to 200°C at a rate of 1°C / min, and held at this temperature for 28 hours.

[0038] The washing process in step five involves first washing with dilute hydrochloric acid and then washing with deionized water until neutral.

[0039] The drying process in step five involves drying at 80°C for 8 hours.

[0040] In step five, the hydrothermal reactor is filled to 70%.

[0041] like Figure 1 As shown, the powder obtained in this embodiment has an overall pecan-like morphology with a size of about 1μm×2μm. The pecan-like shape is formed by the assembly of multiple monomers, and there are obvious grooves between the monomers. At the same time, there are a few pits inside the monomers.

[0042] like Figure 2 As shown in the enlarged view of the powder obtained in this embodiment, a large number of nanocrystals are densely distributed on the surface of the pecan-shaped particles, presenting a fluffy appearance.

[0043] like Figure 3 As shown, the powder prepared in this embodiment was subjected to X-ray diffraction analysis. The position and intensity of its characteristic peaks coincided with those of barium titanate, and no other crystalline phase impurity peaks were present, indicating that the product was barium titanate and had good crystallization properties.

[0044] like Figure 4 As shown, the powder prepared in this embodiment has a complete crystal structure, and the monomer crystallinity of the assembled pecan-shaped powder is good. EDS analysis further shows that the pecan-shaped powder is composed of Ba, Ti and O elements.

[0045] like Figure 5 As shown, the powder prepared in this embodiment is at a concentration of 10 mg / L. -1 The graph shows the relationship between the piezoelectric catalytic degradation rate and time under ultrasonic vibration when Congo Red (CR) is the degradation target. After 180 min of ultrasonic vibration, the CR degradation rate reached 96.2%, indicating that the material has good piezoelectric catalytic performance.

[0046] like Figure 6 As shown, the powder prepared in this embodiment is at a concentration of 10 mg / L. -1 The graph shows the relationship between the photocatalytic degradation rate and time under illumination when Congo Red (CR) is the degradation target. After 180 minutes of illumination, the CR degradation rate reached 98.2%, indicating that the material has good photocatalytic performance.

[0047] like Figure 7As shown, the powder prepared in this embodiment is at a concentration of 10 mg / L. -1 The graph shows the piezoelectric-photocatalytic degradation rate versus time under ultrasonic vibration and light irradiation when Congo Red (CR) is the degradation target. After 180 minutes of combined ultrasonic and light excitation, the degradation rate of CR reached 99.9%, indicating that the material has good piezoelectric-photocatalytic performance. Furthermore, compared with piezoelectric and photocatalytic performance, its piezoelectric-photocatalytic performance has a significant advantage in degradation rate and exhibits a good synergistic effect, suggesting that this material can broaden the energy utilization range and improve energy utilization efficiency.

[0048] like Figure 8 As shown in the stability spectrum of the piezoelectric-photocatalytic performance of the powder prepared in the embodiment of the present invention, after five cycles of testing, its degradation rate remained at 97.2% compared to 99.9% in the first cycle, showing good performance stability. This is mainly attributed to the good recovery characteristics of the micro-nano structure powder. Example 2

[0049] A method for preparing pecan-shaped barium titanate powder with nanocrystals on its surface, characterized by comprising the following steps:

[0050] Step 1: Add the barium chloride dihydrate solution prepared by 0.25g barium chloride dihydrate, 5g ethanol and 45g water to a transparent 1g PEG40000 solution, and stir continuously at room temperature for 1h to obtain a uniform and clear barium-polymer integration precursor solution.

[0051] Step 2: Tetrabutyl titanate was gradually added dropwise to the ethanol solution. After stirring and aging for 30 minutes, a pale yellow titanium source solution with a volume of 9 ml and a concentration of 1 mol / L was obtained.

[0052] Step 3: Under vigorous stirring at 600 rpm, the above pale yellow titanium source solution was slowly added dropwise to the barium-polymer integration precursor solution at a rate of 0.5 ml / min using a constant flow pump to obtain a milky white suspension. After standing for 10 min, the solid and liquid were separated, with the upper layer being clear liquid and the lower layer being a white precipitate.

[0053] Step 4: Slowly add 10g of 9mol / L NaOH solution to the above solid-liquid separation suspension to obtain the hydrothermal reaction precursor solution;

[0054] Step 5: The precursor solution is loaded into a hydrothermal reactor for a staged hydrothermal reaction. After the reaction, the product is separated, washed, and dried to obtain pecan-shaped barium titanate powder.

[0055] The heating regime for the staged hydrothermal reaction process in step five is as follows: first, the temperature is raised from room temperature to 160°C at a rate of 2°C / min, and held at this temperature for 2 hours; then, the temperature is raised to 220°C at a rate of 1°C / min, and held at this temperature for 20 hours.

[0056] The washing process in step five involves first washing with dilute hydrochloric acid and then washing with deionized water until neutral.

[0057] The drying process in step five involves drying at 90°C for 4 hours.

[0058] In step five, the hydrothermal reactor is filled to 70%. Example 3

[0059] A method for preparing pecan-shaped barium titanate powder with nanocrystals on its surface, characterized by comprising the following steps:

[0060] Step 1: Add the barium chloride dihydrate solution prepared by 0.245g barium chloride dihydrate, 5g ethanol and 43g water to a transparent 1g PEG40000 solution, and stir continuously at room temperature for 1h to obtain a uniform and clear barium-polymer integration precursor solution.

[0061] Step 2: Tetrabutyl titanate was gradually added dropwise to the ethanol solution. After stirring and aging for 30 minutes, a pale yellow titanium source solution with a volume of 11 ml and a concentration of 1 mol / L was obtained.

[0062] Step 3: Under vigorous stirring at 600 rpm, the above pale yellow titanium source solution was slowly added dropwise to the barium-polymer integration precursor solution at a rate of 0.5 ml / min using a constant flow pump to obtain a milky white suspension. After standing for 10 min, the solid and liquid were separated, with the upper layer being clear liquid and the lower layer being a white precipitate.

[0063] Step 4: Slowly add 12g of 9mol / L NaOH solution to the above solid-liquid separation suspension to obtain the hydrothermal reaction precursor solution;

[0064] Step 5: The precursor solution is loaded into a hydrothermal reactor for a staged hydrothermal reaction. After the reaction, the product is separated, washed, and dried to obtain pecan-shaped barium titanate powder.

[0065] The heating regime for the staged hydrothermal reaction process in step five is as follows: first, the temperature is raised from room temperature to 160°C at a rate of 2°C / min, and held at this temperature for 2 hours; then, the temperature is raised to 210°C at a rate of 1°C / min, and held at this temperature for 25 hours.

[0066] The washing process in step five involves first washing with dilute hydrochloric acid and then washing with deionized water until neutral.

[0067] The drying process in step five involves drying at 85°C for 6 hours.

[0068] In step five, the hydrothermal reactor is filled to 70%.

[0069] The above embodiments are merely illustrative of the principles and effects of the present invention, as well as some examples of its application, and are not intended to limit the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention.

Claims

1. A method for preparing pecan-shaped barium titanate powder with nanocrystals on its surface, characterized in that... Includes the following steps: Step 1: Add the barium chloride dihydrate solution prepared by barium chloride dihydrate, ethanol, and water to the transparent PEG solution and stir continuously at room temperature to obtain a uniform and clear barium-polymer integration precursor solution. Step 2: Tetrabutyl titanate is gradually added dropwise to the ethanol solution, and after stirring and aging, a pale yellow titanium source solution is obtained; Step 3: Under vigorous stirring, the above pale yellow titanium source solution is slowly added dropwise to the barium-polymer integration precursor solution using a constant flow pump to obtain a milky white suspension, which is then separated into solid and liquid components after standing. Step 4: Slowly add a reaction promoter to the above solid-liquid separation suspension to obtain a hydrothermal reaction precursor solution; Step 5: The precursor solution is subjected to a fractional hydrothermal reaction. After the reaction, the product is separated, washed, and dried to obtain pecan-shaped barium titanate powder. The heating regime for the graded hydrothermal reaction process in step five is as follows: first, the temperature is raised from room temperature to 160°C at a rate of 2°C / min, and held at this temperature for 2 hours; then, the temperature is raised to 200-220°C at a rate of 1°C / min, and held at this temperature for 20-28 hours. In step four, the reaction promoter is a 9 mol / L NaOH solution, and the amount added is 10-15 g.

2. The preparation method according to claim 1, characterized in that: In step one, the mass of barium chloride dihydrate, ethanol, and water are 0.24–0.25 g, 5 g, and 40–45 g, respectively; the average molecular weight of the PEG solution is 40,000, and its mass is 1 g.

3. The preparation method according to claim 1, characterized in that: In step two, the concentration of the pale yellow titanium source solution is 1 mol / L, the volume is 9-11 ml, and the aging time is 30 min.

4. The preparation method according to claim 1, characterized in that: In step three, the stirring speed is 600 rpm and the constant flow pump drip rate is 0.5 ml / min. After solid-liquid separation, the upper layer is clear liquid and the lower layer is white precipitate.

5. The preparation method according to claim 1, characterized in that: The washing process in step five involves first washing with dilute hydrochloric acid and then washing with deionized water until neutral.

6. The preparation method according to claim 1, characterized in that: The drying process in step five involves drying at 80–90°C for 4–8 hours.

7. The preparation method according to claim 1, characterized in that: In step five, the hydrothermal reactor is filled to 70%.

8. The preparation method according to claim 1, characterized in that: In step five, the walnut-shaped barium titanate powder has a size of 1μm×2μm, with grooves inside the monomer and a surface rich in nanocrystals.

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