Depolymerization method of hard agglomerated barium titanate nano-powder

Abstract

The invention relates to a depolymerization method of hard agglomerated barium titanate nano-powder. The depolymerization method of the hard agglomerated barium titanate nano-powder comprises the following steps: adding the hard agglomerated barium titanate nano-powder, zirconium oxide balls, a dispersing agent and absolute ethyl alcohol into a dispersing tank, and then dispersing to obtain slurry; drying and sieving are carried out, such that depolymerized barium titanate nano-powder is obtained; wherein the size of the zirconium oxide balls is 800-1200 times of the average particle size of the hard agglomerated barium titanate nano-powder.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic functional powder material dispersion, and particularly relates to a method for depolymerizing hard-aggregated barium titanate nano-powders. Background Art

[0002] With the continuous development of the modern electronic technology field, the market demand for high-performance electronic components and materials is also increasing day by day. Barium titanate (BaTiO3), as an inorganic functional material, has been highly favored due to its excellent dielectric properties and various electrical characteristics. Barium titanate materials have a wide range of applications in electronic devices, such as multilayer ceramic capacitors (MLCCs), embedded capacitors, electro-optic devices, and optical memory storage devices, etc.

[0003] Barium titanate powders for high-performance MLCCs have strict requirements on crystal phase, grain size, morphology, and dispersibility, etc. For example, the crystal phase is a pure tetragonal phase, the particle size is nanoscale, the particle size is uniform, and the particle dispersibility is good. At present, most of the barium titanate produced in China is medium and low-end powders, with serious agglomeration and poor dispersibility. Using barium titanate powders with serious agglomeration as raw materials and obtaining ceramics through high-temperature heat treatment, their performance will be greatly reduced because the existence of agglomeration will lead to problems such as reduced powder activity, increased doping difficulty, and decreased ceramic density. Therefore, in-depth research on the depolymerization method of barium titanate will help to obtain high-quality barium titanate nano-powders.

[0004] In Patent US20160074826A1, by flowing a slurry containing agglomerated powders into a container, then flowing through a tiny gap formed between a stator and a rotor, and then irradiating with ultrasonic waves, the agglomerated powders are subjected to the effects of compression, expansion, and shear, so as to crush the materials. However, since the distance between the stator and the rotor is in the millimeter level, this method is not applicable to the dispersion of barium titanate agglomerated powders with an average particle size less than 1 μm. In the depolymerization method disclosed in Patent CN101961616B, the slurry containing agglomerated powders is sprayed from a small hole towards a baffle block, and the slurry is subjected to intense impact, friction, and shear, etc. during the rapid turbulent flow and high-speed impact atomization process, achieving the effects of breaking, emulsifying, and homogenously dispersing the agglomerated nano-materials. However, the intense force generated by this depolymerization method will cause some particles to be damaged and some hard agglomerations to remain unopened. Patent CN110833790A combines stirring and ultrasonic waves, irradiating with ultrasonic waves while stirring the slurry at a high speed, so that the agglomerated powder materials are opened and dispersed. However, the depolymerization force generated by this method is weak, and it is difficult to achieve a good dispersion effect on hard agglomerates. Summary of the Invention

[0005] Aiming at the problem of poor depolymerization effect of hard agglomerates in the above-mentioned barium titanate nano-powders, the present invention provides a method for depolymerizing hard-aggregated barium titanate nano-powders.

[0006] Specifically, the present invention provides a method for depolymerizing hard-aggregated barium titanate nanometer powder. The depolymerization method comprises the following steps: adding the hard-aggregated barium titanate nanometer powder, zirconia balls, a dispersant and absolute ethanol into a dispersion tank, and then performing dispersion to obtain a slurry; through drying and sieving, the depolymerized barium titanate nanometer powder is obtained. Among them, the size of the zirconia balls is 800-1200 times the average particle size of the hard-aggregated barium titanate nanometer powder.

[0007] Preferably, the filling ratio of the zirconia balls in the dispersion tank is 20-50%, preferably 30-40%.

[0008] Preferably, the dispersant is one or more of triethylhexyl phosphate, methyl pentanol, cellulose derivatives, polyacrylamide, polyoxyalkylene compounds, guar gum, and fatty acid polyethylene glycol esters.

[0009] Preferably, the solid content of the slurry is 5-70 wt%, preferably 20-40 wt%.

[0010] Preferably, the dosage of the dispersant is 0.5-5% of the mass of the hard-aggregated barium titanate nanometer powder, preferably 1.5-2.5%.

[0011] Preferably, the dispersion time is 1-6 h, preferably 2-4 h; the dispersion rotation speed is 100-500 r / min, preferably 300-400 r / min.

[0012] Preferably, the drying method is one of oven drying, microwave drying, freeze drying, spray drying, and supercritical drying.

[0013] Preferably, the average particle size of the depolymerized barium titanate nanometer powder is 50-500 nm.

[0014] Beneficial effects The depolymerization method provided by the present invention can open the hard aggregation of barium titanate nanometer powder without damaging the integrity of the barium titanate nanometer powder; moreover, the equipment required for opening the hard aggregation of barium titanate nanometer powder adopted by the present invention is simple to operate and has a low cost. Description of the drawings

[0015] Figure 1 is the scanning electron microscope image of the hard-aggregated barium titanate nanometer powder in Example 3, Example 4, Example 5, Comparative Example 2, and Comparative Example 3; Figure 2 is the scanning electron microscope image of the depolymerized barium titanate nanometer powder in Example 5; Figure 3 is the scanning electron microscope image of the depolymerized barium titanate nanometer powder in Comparative Example 2; Figure 4 Scanning electron micrograph of the depolymerized barium titanate nanopowder in Comparative Example 3. Specific embodiments

[0016] The present invention will be further illustrated by the embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and do not limit the present invention.

[0017] Hereinafter, a method for depolymerizing hard-aggregated barium titanate nanopowder provided by the present invention will be exemplarily described. The depolymerization method may include the following steps: adding the hard-aggregated barium titanate nanopowder, zirconia balls, a dispersant, and absolute ethanol into a dispersion tank, and then performing dispersion to obtain a slurry; drying and sieving to obtain the depolymerized barium titanate nanopowder.

[0018] The average value of the particle size is obtained by statistically analyzing the particle size of the hard-aggregated barium titanate nanopowder.

[0019] The introduction of impurities can be reduced by using zirconia balls. In some embodiments, the filling ratio of the zirconia balls in the dispersion tank can be controlled to be 20-50%, preferably 30-40%. If the filling ratio is too small, the dispersion efficiency is low; if the filling ratio is too large, the wear between the zirconia balls will increase, resulting in an increase in impurities.

[0020] By analyzing the factors affecting depolymerization, the present invention obtains the optimal size range of zirconia balls for dispersion. The zirconia balls perform a dropping motion under the action of centrifugal force, generating collision and shear forces. The magnitudes of the collision and shear forces need to be controlled within an appropriate range. If they are too small, the hard aggregates of barium titanate cannot be depolymerized; if they are too large, the barium titanate particles will be damaged. The main influencing factor for the magnitudes of the collision and shear forces is the size of the zirconia balls. The larger the zirconia balls, the greater the mass and the greater the generated forces.

[0021] According to the motion characteristics of the zirconia balls, the following formula is obtained: R1≤R≤R2 (3) Among them, R1: the minimum size of zirconia balls that can effectively depolymerize hard-aggregated barium titanate nano-powder, unit: mm; R2: the maximum size of zirconia balls that can be used (if exceeded, the integrity of barium titanate nano-powder particles will be damaged), unit: mm; R: the size of zirconia balls that can be used for depolymerizing hard-aggregated barium titanate nano-powder; E: Young's modulus of barium titanate nano-powder, unit: Pa; ε1: strain at fracture of hard aggregates in barium titanate nano-powder; ε2: strain at fracture of the bulk of barium titanate nano-powder; L: average width of the joints of hard aggregates in barium titanate nano-powder, unit: nm; r: primary average particle size of hard-aggregated barium titanate nano-powder, unit: nm; ρ: density of zirconia balls, unit: g / cm 3 ; V: the maximum speed of zirconia ball movement during dispersion, unit: m / s.

[0022] According to formulas (1), (2), and (3), the size (diameter) of the zirconia balls can be controlled to be 800 - 1200 times the average particle size of the hard-aggregated barium titanate nano-powder. If the size of the zirconia balls is too small, the hard aggregates of barium titanate cannot be opened; if the size of the zirconia balls is too large, the hard aggregates of barium titanate can be opened, but the barium titanate particles will be damaged.

[0023] In some embodiments, the dispersant can be one or more of triethylhexyl phosphate, methylpentanol, cellulose derivatives, polyacrylamide, polyoxyalkylene compounds, guar gum, fatty acid polyethylene glycol esters.

[0024] In some embodiments, the solid content of the slurry (mass fraction of hard-aggregated barium titanate nano-powder in the slurry) can be controlled to be 5 - 70 wt%, preferably 20 - 40 wt%. If the solid content is too low, the dispersion efficiency is low; if the solid content is too high, the fluidity of the slurry is poor and the dispersion effect is uneven.

[0025] In some embodiments, the dosage of the dispersant can be controlled to be 0.5 - 5% of the mass of the hard-aggregated barium titanate nano-powder, preferably 1.5 - 2.5%. If the dosage of the dispersant is too low, the depolymerized barium titanate nano-powder will quickly re-aggregate again, and the dispersion efficiency will decrease; if the dosage of the dispersant is too high, it will cause the viscosity of the slurry to increase and the dispersion effect to be uneven.

[0026] In some embodiments, the dispersion time can be 1 - 6 h, preferably 2 - 4 h; the dispersion rotation speed can be 100 - 500 r / min, preferably 300 - 400 r / min. If the dispersion time is too short and the rotation speed is too low, the hard aggregates of barium titanate cannot be opened; if the dispersion time is too long and the rotation speed is too high, the hard aggregates of barium titanate can be opened, but the barium titanate particles are easily damaged.

[0027] In some embodiments, the drying method may be one of oven drying, microwave drying, freeze drying, spray drying, and supercritical drying.

[0028] In some embodiments, the average particle size of the depolymerized barium titanate nanopowder may be 50 - 500 nm.

[0029] In the present invention, zirconia balls perform a dropping motion under the action of centrifugal force, and the generated collision and shear forces depolymerize and disperse the hard-aggregated barium titanate nanopowder. Meanwhile, by controlling the size of the zirconia balls, the magnitude of the acting force can be regulated, opening the hard aggregates without damaging the particle integrity, thereby obtaining a well-dispersed barium titanate nanopowder with undamaged particles.

[0030] For the dispersed barium titanate nanopowder, the depolymerization effect can be evaluated from two aspects: the dispersion degree and integrity of the nanopowder particles.

[0031] Particle dispersibility. The depolymerized barium titanate nanopowder is characterized by scanning electron microscopy (SEM). Adjust the appropriate magnification so that the number of complete barium titanate particles in the SEM image is not less than 300. Count the percentage of barium titanate particles still in the hard-aggregated state among all particles. If this ratio is less than 10%, it is recorded as "○"; if it is greater than or equal to 10%, it is recorded as "×".

[0032] Particle integrity. The depolymerized barium titanate nanopowder is characterized by scanning electron microscopy (SEM). Adjust the appropriate magnification so that the number of complete barium titanate particles in the SEM image is not less than 300. Count the percentage of damaged barium titanate particles among all particles. If this ratio is less than 10%, it is recorded as "○"; if it is greater than or equal to 10%, it is recorded as "×".

[0033] The following further lists examples to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Those skilled in the art's non-essential improvements and adjustments based on the above content of the present invention all fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range according to the description herein, rather than being limited to the specific values in the following examples.

[0034] Example 1

[0035] The method for depolymerizing the hard-aggregated barium titanate nanopowder provided in this example is as follows: Add zirconia balls with a size of 0.1 mm (100000 nm) to the dispersion tank to make the filling ratio 40%; add hard-aggregated barium titanate nano-powder with an average particle size of 100 nm to the dispersion tank. Based on the mass of the added hard-aggregated barium titanate nano-powder being 100 wt%, add 2 wt% of a polyoxyalkylene compound dispersant to the dispersion tank; then add absolute ethanol to make the solid content of the slurry 30 wt%; disperse at a speed of 300 r / min for 2 h, and after drying and sieving, obtain the depolymerized barium titanate nano-powder.

[0036] Example 2

[0037] The method for depolymerizing the hard-aggregated barium titanate nano-powder provided in this example refers to Example 1. The main difference is that the dispersion speed is 400 r / min.

[0038] Example 3

[0039] The method for depolymerizing the hard-aggregated barium titanate nano-powder provided in this example refers to Example 1. The main difference is that the size of the zirconia balls is 0.2 mm, and the average particle size of the hard-aggregated barium titanate nano-powder is 200 nm.

[0040] Example 4

[0041] The method for depolymerizing the hard-aggregated barium titanate nano-powder provided in this example refers to Example 1. The main difference is that the size of the zirconia balls is 0.2 mm, the average particle size of the hard-aggregated barium titanate nano-powder is 200 nm, and the dispersion time is 4 h.

[0042] Example 5

[0043] The method for depolymerizing the hard-aggregated barium titanate nano-powder provided in this example refers to Example 1. The main difference is that the size of the zirconia balls is 0.2 mm, the average particle size of the hard-aggregated barium titanate nano-powder is 200 nm, and the dispersion speed is 400 r / min.

[0044] Figure 1 SEM images of the hard-aggregated barium titanate nano-powder in Example 3, Example 4, Example 5, Comparative Example 2, and Comparative Example 3. It can be seen from the figure that all the barium titanate nano-powders are in a hard-aggregated state.

[0045] Figure 2 SEM image of the depolymerized barium titanate nano-powder in Example 5. It can be seen from the figure that most of the barium titanate nano-powders are depolymerized, and the integrity of the powder particles is good.

[0046] Example 6

[0047] The method for depolymerizing the hard-aggregated barium titanate nanopowder provided in this example refers to Example 1, and the main difference is that the size of the zirconia balls is 0.3 mm, and the average particle size of the hard-aggregated barium titanate nanopowder is 300 nm.

[0048] Example 7

[0049] The method for depolymerizing the hard-aggregated barium titanate nanopowder provided in this example refers to Example 1, and the main differences are that the size of the zirconia balls is 0.3 mm, the average particle size of the hard-aggregated barium titanate nanopowder is 300 nm, and the dispersion time is 4 h.

[0050] Example 8

[0051] The method for depolymerizing the hard-aggregated barium titanate nanopowder provided in this example refers to Example 1, and the main differences are that the size of the zirconia balls is 0.3 mm, the average particle size of the hard-aggregated barium titanate nanopowder is 300 nm, and the dispersion speed is 400 r / min.

[0052] Comparative Example 1

[0053] The method for depolymerizing the hard-aggregated barium titanate nanopowder provided in this comparative example refers to Example 1, and the main difference is that the size of the zirconia balls is 0.3 mm and the dispersion speed is 400 r / min.

[0054] For the barium titanate nanopowder after depolymerization obtained in this comparative example, the particle dispersion is good, but the particle integrity is poor.

[0055] Comparative Example 2

[0056] The method for depolymerizing the hard-aggregated barium titanate nanopowder provided in this comparative example refers to Example 1, and the main differences are that the average particle size of the hard-aggregated barium titanate nanopowder is 200 nm and the dispersion speed is 400 r / min.

[0057] Figure 3 It is the scanning electron microscope image of the barium titanate nanopowder after depolymerization in Comparative Example 2. It can be seen from the figure that most of the barium titanate nanopowders are still in the hard-aggregated state.

[0058] Comparative Example 3

[0059] The method for depolymerizing the hard-aggregated barium titanate nanopowder provided in this comparative example refers to Example 1, and the main differences are that the size of the zirconia balls is 0.5 mm, the average particle size of the hard-aggregated barium titanate nanopowder is 200 nm, and the dispersion speed is 400 r / min.

[0060] Figure 4 It is the scanning electron microscope image of the barium titanate nanopowder after depolymerization in Comparative Example 3. It can be seen from the figure that most of the barium titanate nanopowders are damaged.

[0061] Comparative Example 4

[0062] The method for depolymerizing the hard-aggregated barium titanate nanometer powder provided in this comparative example refers to Example 1. The main difference is that the average particle size of the hard-aggregated barium titanate nanometer powder is 300 nm, and the dispersion rotation speed is 400 r / min.

[0063] The depolymerized barium titanate nanometer powder obtained in this comparative example has poor particle dispersibility but good particle integrity.

[0064] Comparative Example 5

[0065] The method for depolymerizing the hard-aggregated barium titanate nanometer powder provided in this comparative example refers to Example 1. The main differences are that the size of the zirconia balls for dispersion is 0.5 mm, the average particle size of the hard-aggregated barium titanate nanometer powder is 300 nm, and the dispersion rotation speed is 400 r / min.

[0066] The depolymerized barium titanate nanometer powder obtained in this comparative example has good particle dispersibility but poor particle integrity.

[0067] The evaluation of the depolymerization effects of Examples 1-8 and Comparative Examples 1-5 is shown in the following table:

[0068] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and substitutions of the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A method for depolymerizing hard-aggregated barium titanate nanometer powder, characterized in that, The depolymerization method comprises the following steps: adding hard-aggregated barium titanate nanometer powder, zirconia balls, a dispersant and absolute ethanol into a dispersion tank, and then performing dispersion to obtain a slurry; drying and sieving to obtain the depolymerized barium titanate nanometer powder; Among them, the size of the zirconia balls is 800-1200 times the average particle size of the hard-aggregated barium titanate nanometer powder.

2. The depolymerization method according to claim 1, characterized in that The filling ratio of the zirconia balls in the dispersion tank is 20-50%, preferably 30-40%.

3. The depolymerization method according to claim 1 or 2, characterized in that, The dispersant is one or more of triethylhexyl phosphate, methyl pentanol, cellulose derivatives, polyacrylamide, polyoxyalkylene compounds, guar gum, and fatty acid polyethylene glycol esters.

4. The depolymerization method according to any one of claims 1-3, characterized in that The solid content of the slurry is 5-70 wt%, preferably 20-40 wt%.

5. The depolymerization method according to any one of claims 1-4, characterized in that, The dosage of the dispersant is 0.5-5% of the mass of the hard-aggregated barium titanate nanometer powder, preferably 1.5-2.5%.

6. The depolymerization method according to any one of claims 1-5, characterized in that, The dispersion time is 1-6 h, preferably 2-4 h; the dispersion rotation speed is 100-500 r / min, preferably 300-400 r / min.

7. The depolymerization method according to any one of claims 1-6, characterized in that, The drying method is one of oven drying, microwave drying, freeze drying, spray drying and supercritical drying.

8. The depolymerization method according to any one of claims 1-7, characterized in that, The average particle size of the depolymerized barium titanate nanometer powder is 50-500 nm.

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