KR20210153705A - Nano barium titanate microcrystals and their manufacturing method, and barium titanate powder and their manufacturing method - Google Patents

Abstract

Provided are microcrystals of nano barium titanate and a method for manufacturing the same, and barium titanate powder and a method for manufacturing the same. In the method for producing nano barium titanate microcrystals, the aqueous solution of nano titanium dioxide having a mass concentration of 20% or more and an aqueous solution of barium hydroxide are rapidly mixed, and the temperature of the obtained mixing system is obtained by rapidly mixing both of the aqueous solution of barium hydroxide. lowering the temperature by 2°C; In an inert atmosphere, the mixture system is subjected to atmospheric pressure hydrothermal synthesis reaction at 90 to 110° C., and the reaction product is collected, washed and dried to obtain nano barium titanate microcrystals. High-quality barium titanate powder can be obtained by firing the nano-barium titanate microcrystals as a raw material.

Description

Nano barium titanate microcrystals and their manufacturing method, and barium titanate powder and their manufacturing method

The present invention relates to nanomaterial technology, and more particularly, to nano-barium titanate microcrystals and a method for producing the same, and barium titanate powder and a method for producing the same.

Since barium titanate (BaTiO ₃ ) has excellent dielectric, ferroelectric and piezoelectric performance, it is widely used in the electric ceramic industry, and is widely used in multilayer ceramic capacitors (MLCC), positive temperature coefficient thermistors (PTC), and dynamic random access memory (DRAM). It is a basic material for manufacturing electronic elements.

Currently, the mainly used process for producing nano barium titanate powder generally includes a solid-phase sintering method and a liquid-phase synthesis method, where the liquid-phase synthesis method additionally includes a sol-gel method, a co-precipitation method, and a hydrothermal method. In the solid-state sintering method, oxides or acid salts of the metal elements (Ti and Ba) constituting barium titanate are mixed and polished, and then calcined at a high temperature of 1100° C. left and right, and a desired powder is formed through a solid-phase reaction. The solid-state sintering method has a simpler process, but the particles of the prepared powder easily aggregate, have a large particle size, have a high impurity content, and have poor material uniformity, so it cannot satisfy the demand for high performance and miniaturization of electronic elements. The powder prepared by the sol-gel method and the co-precipitation method has high purity and small particle size, but the process is complicated and the raw material cost is high, so there is a difficulty in realizing industrial production.

The hydrothermal method can also be divided into a high-pressure hydrothermal method and an atmospheric pressure hydrothermal method. The high-pressure hydrothermal method performs hydrothermal treatment on a Ba(OH) _{2 aqueous solution containing dispersed TiO 2} fine particles in a closed system such as a high-pressure reactor, and at a constant temperature and self-generated pressure of water, barium titanate powder is obtained. . Under high-temperature, high-pressure hydrothermal conditions, it provides a special physicochemical environment that cannot be obtained under atmospheric conditions, so that the precursor is sufficiently dissolved in the reaction system to reach a certain degree of supersaturation, so that nucleation crystallization occurs to form powder or nano make a decision Therefore, the barium titanate powder produced by the high-pressure hydrothermal method has advantages such as high purity, high crystallinity, small particle size, and uniform distribution of particles, and can achieve eco-friendly raw materials. However, since the hydrothermal reaction is carried out under high temperature, high pressure and closed conditions, it consumes a lot of energy in the reaction process, has low safety, and can only be produced in a lot, but large-scale continuous production is impossible; In addition, since the reaction is carried out in an alkaline condition and a high-temperature and high-pressure environment, the demands on the reactor are higher, and the costs such as equipment input and operation requirements are also very high.

Atmospheric pressure hydrothermal method generally uses a titanium metal organic compound such as tetrabutyl titanate as a titanium source, barium hydroxide as a barium source, and an alcohol-like substance such as n-butanol as a solvent. Allow conversion and production of barium titanate to occur. Since the atmospheric pressure hydrothermal method is carried out at normal pressure and at a low temperature of 50∼110°C, the requirements for the device are simple, more secure, and industrialization can be realized more easily, and it is more mature now. However, in previous studies, barium titanate particles produced by atmospheric pressure hydrothermal method have a larger particle size, generally 100 nm or more, and the particle size distribution is not concentrated and dispersibility is poor. cannot satisfy the high-quality demand for

Therefore, developing a production process for nano barium titanate microcrystals based on the atmospheric pressure hydrothermal method to obtain high quality barium titanate powder and to obtain higher production efficiency remains a task to be solved at present.

In order to solve the above-described defects according to the prior art, the present invention provides a method for manufacturing nano barium titanate microcrystals, and the nano barium titanate microcrystals prepared through the atmospheric pressure hydrothermal synthesis process have a smaller particle size, and the particle size distribution is uniform, has high purity, has a very high yield, and can be used as a raw material for high-quality barium titanate powder.

The present invention further provides nano barium titanate microcrystals, manufactured by the above-described manufacturing method, wherein the nano barium titanate microcrystals have small particle sizes, uniform particle size distribution, high purity, and high quality barium titanate. It can be used as a raw material for the production of powder.

The method for producing barium titanate powder provided in the present invention can produce nano barium titanate powder having high purity, excellent crystallinity and dispersibility, and having a small particle size by using the above-described nano barium titanate microcrystals as a raw material, It has a very high yield.

The present invention further provides barium titanate powder, which is produced by the above-described manufacturing method, wherein the barium titanate powder has a small particle size and controllable, high purity, excellent crystallinity and dispersibility, and a very high yield. have

In order to achieve the above object, the present invention provides a method for producing nano barium titanate microcrystals, the method comprising:

Rapidly mixing the nano titanium dioxide aqueous dispersion having a lower temperature and an aqueous solution of barium hydroxide having a higher temperature so that the temperature of the obtained mixing system is lower than the temperature of the aqueous barium hydroxide solution by 2°C by rapid mixing of both; Here, the mass concentration of the nano titanium dioxide aqueous dispersion is 20% or more;

In an inert atmosphere, the mixture system proceeds the atmospheric pressure hydrothermal synthesis reaction at 90 to 110° C., and collecting, washing and drying the reaction product to obtain nano barium titanate microcrystals.

When producing nano barium titanate powder using the conventional atmospheric pressure hydrothermal synthesis method, if the TiO ₂ concentration as the titanium source is high, the particle size of the nano barium titanate powder is larger, the particle size distribution is not concentrated, and agglomeration between the particles You'll get rid of the extremely severe punctuation; When _{the concentration of TiO 2} is too low, the production efficiency is lowered, and the particle size of the barium titanate particles is larger than that of the particles. In view of this situation, the present invention proposes a solution, in which a high concentration (mass concentration ≥ 20%) aqueous nano titanium dioxide dispersion is used as a raw material, and first, an aqueous nano titanium dioxide dispersion and an aqueous barium hydroxide solution are rapidly mixed. Then, by performing atmospheric pressure hydrothermal synthesis, it is possible to reduce the amount of solvent used in the atmospheric pressure hydrothermal synthesis reaction process, improve production efficiency, achieve large-scale continuous production, and the obtained nano barium titanate microcrystalline particles have a small particle size With advantages such as uniformity and high purity, it is possible to obtain a barium titanate powder with better crystal growth by using the nano-barium titanate microcrystals as a raw material, through calcination or other means, and the barium titanate powder It has small particle size, uniform particle size distribution, high purity, and excellent dispersibility.

The rapid mixing between the aqueous nano titanium dioxide dispersion and the aqueous barium hydroxide solution, or the rapid mixing of the titanium source and the barium source, is indicated by the degree of temperature drop of the mixing system, that is, directly caused by the rapid mixing of both. A significant decrease in the temperature to be used is not included in the significant decrease in temperature by means such as external cooling during the mixing process. In general industrial production, even if their rapid mixing is performed under heating with a heater, since the addition amount of the aqueous titanium dioxide dispersion with a lower temperature is large and the addition rate is fast, the heater cannot maintain the rapid temperature rise of the system. Therefore, the temperature of the mixing system is at least 2°C lower than the temperature of the aqueous barium hydroxide solution before mixing. In the specific implementation process of the present invention, when it is monitored that the temperature of the mixing system has dropped by 2° C. or more during the mixing process, so-called “rapid mixing” is indicated. For example, when nano titanium dioxide aqueous dispersion is rapidly added to barium hydroxide aqueous solution, the temperature of the barium hydroxide aqueous solution mixing system is significantly lowered, and when the temperature drop reaches 2℃ or more, “rapid mixing” thereof is reached. considered to have been

Of course, the raw material addition or mixing speed must ensure that the temperature of the entire mixed solution is balanced and stabilized as quickly as possible, thereby ensuring the consistency of the growth size of the barium titanate particles thereafter. In actual industrial production, generally high-efficiency mixers and high-speed liquid addition equipment are used, or an on-line type continuous mixer is used so that the aqueous nano titanium dioxide dispersion and the aqueous barium hydroxide solution are rapidly and uniformly mixed. In the process of rapid mixing, in general, a plurality of representative monitoring points can be selected to test the temperature change during the mixing process, and it is desirable that the temperature of each monitoring point is lowered by 2℃ or more and the reduction is basically the same do.

Furthermore, for the subsequent consistency of the growth size of the barium titanate particles, it is preferable that the temperature difference between the temperature of the mixed system and the aqueous barium hydroxide solution is not too large. Controlled in °C. Thereby, it is also possible to effectively prevent the barium source from being deposited due to the temperature jump and drop.

The above-described mixing system may be formulated in an atmospheric environment. Of course, in order to prevent additional side reactions from occurring, the mixing system may also be mixed in an inert atmosphere, for example, under the protection of an inert gas such as nitrogen gas or argon gas.

Specifically, the blending of the above-mentioned mixing system can be completed by adding the aqueous nano titanium dioxide dispersion to the aqueous barium hydroxide solution, and can be completed by adding the aqueous barium hydroxide aqueous solution to the aqueous nano titanium dioxide dispersion, or the aqueous nano titanium dioxide dispersion It can also be completed by mixing an aqueous solution of barium hydroxide with parallel heat.

In a preferred embodiment of the present invention, an aqueous dispersion of nano titanium dioxide having a lower temperature is added to an aqueous solution of barium hydroxide having a higher temperature and mixed rapidly, so that the temperature of the obtained mixing system is at least 2° C. compared to the temperature of the aqueous barium hydroxide solution , for example, 2 to 20 °C, further 2 to 10 °C lower. If the mixing system is mixed using this method, it is independent of the input and transportation of raw materials for the high-temperature aqueous barium hydroxide solution, the requirements for the process and equipment are lower, and it can be implemented more easily.

It can be understood that the raw material nano titanium dioxide preferably has a smaller particle size, and is advantageous to obtain nano barium titanate microcrystals and barium titanate powder having smaller particle sizes. In general, in the aqueous dispersion of nanotitanium dioxide used, the median particle diameter of nanotitanium dioxide calculated based on volume is D50≤30nm. The average particle diameter of the nano-barium titanate microcrystals thus prepared is generally 10 to 30 nm, and the particle size distribution is more uniform. In addition, the main phase of the nano barium titanate microcrystals is a cubic phase, and the cubic phase content may even reach 100%. On the other hand, the nano-barium titanate microcrystals also have high purity and excellent dispersibility.

The aqueous dispersion of nano titanium dioxide used in the present invention is formed by dispersing nano titanium dioxide powder in water. The present invention is not particularly limited with respect to the source of the nano titanium dioxide powder or nano titanium dioxide aqueous dispersion, and may be purchased from the market or prepared by itself. For example, after preparing nano titanium dioxide powder according to the process described in the patent application 201610879270.3 or 201610879701.6, it is dispersed in deionized water according to the ratio to obtain an aqueous nano titanium dioxide dispersion.

By rationally controlling the concentration of the aqueous nano titanium dioxide dispersion, it is advantageous to prevent problems such as agglomeration of nano barium titanate microcrystals during the synthesis process. In general, the mass concentration of the aqueous nano titanium dioxide dispersion is set to 20-50%. control Thereby, not only can the nano barium titanate microcrystals have better dispersibility characteristics, but also have the advantages of small particle size, more uniform particle size, and high purity; Furthermore, it is possible to ensure that the nano-barium titanate microcrystals have a very good yield, and is particularly suitable for industrial continuous production.

The present invention is not particularly limited with respect to the temperature of the nano titanium dioxide aqueous dispersion, and it can be obtained by mixing at room temperature (25° C.), and may be heated appropriately to increase the mass concentration of nano titanium dioxide, but the temperature is barium hydroxide It should be lower than the temperature of the aqueous solution. In the specific implementation process of the present invention, the temperature of the aqueous dispersion of nano titanium dioxide does not exceed 50 ° C, and is generally 20 to 50 ° C.

Specifically, since nano-titanium dioxide has a very high concentration (≥20%) in the nano-titanium dioxide aqueous dispersion, in order to achieve a high yield of nano-barium titanate powder, the barium hydroxide aqueous solution contains a high concentration of barium ions The molar ratio between ions and titanium atoms and rapid mixing between the barium source and the titanium source should be ensured, and in general, in an aqueous barium hydroxide solution, the barium source concentration is preferably close to the saturation solubility, for example, the barium source mass concentration is 20% or more, and can even reach 50% to 70% or more, so in order to ensure that the barium source hardly precipitates in the aqueous barium hydroxide solution, generally the temperature of the aqueous barium hydroxide solution is not lower than 70 ° C. The temperature is controlled at 70~110℃ and additionally at 90~110℃, thereby ensuring the ratio between the barium source and the titanium source.

The blending of the aqueous barium hydroxide solution must be carried out under an inert atmosphere, for example, under the protection of an inert gas such as nitrogen gas.

In an ideal state, when the molar ratio of Ba and Ti is 1, they sufficiently react to form barium titanate and prevent the residue of the raw material. An excess of the titanium source or barium source is more favorable for the reaction to proceed in a positive direction for synthesizing barium titanate, for example, an excess of Ba is advantageous for reducing the content of titanium dioxide impurities in the reaction product, but leaving a large amount of barium As a result, not only results in wastage of the barium source material, but also when collecting the reaction product, if it comes into contact with air, more barium carbonate impurities may be introduced. In consideration of hydrothermal reaction efficiency and economic factors, in general, the molar ratio between Ba and Ti is controlled to be 1~4:1, additionally 1.5~2:1, so that titanium dioxide reacts sufficiently and finally obtained Ensure that the nano barium titanate microcrystals have higher purity.

After completing the mixing of the mixed system, the mixed system may be allowed to proceed with an atmospheric pressure hydrothermal synthesis reaction. In general, the mixing system is first stirred so that the temperature reaches 90~110°C, and the effective mixing of the barium source and the titanium source is maintained, and then the mixture is kept warm at that temperature for a certain period of time. Specifically, the time of the atmospheric pressure hydrothermal synthesis reaction is preferably 30 minutes or more.

As a result of the inventor's research, the effect on the size of nano barium titanate microcrystals is not large even if the warming time exceeds 24 hours and the reaction time of atmospheric pressure hydrothermal synthesis is continuously extended. In general, the normal pressure hydrothermal synthesis reaction time is controlled so that it does not exceed 24 hours and additionally 3 to 24 hours.

After the atmospheric pressure hydrothermal synthesis reaction is completed, the temperature is lowered and the reaction product is collected, and then treatment such as washing and drying is performed to obtain high-quality nano barium titanate microcrystals. In the specific practice of the present invention, first, solid and liquid separation is performed on the reaction product by means of suction filtration or the like, and then washed with deionized water or deionized water and ethanol by using deionized water and ethanol. and finally dried at 60 to 90° C. to obtain nano barium titanate microcrystals.

The nano barium titanate microcrystals provided in the present invention are manufactured using the above-described manufacturing method. The nano barium titanate microcrystals provided in the present invention have a very small particle size, and the average particle diameter is 100 nm or less, and even the average particle diameter can reach 5 to 30 nm, and is generally 10 to 30 nm; The particle size of the nano barium titanate microcrystals is basically a normal distribution, and the particle size distribution is narrower; The lattice constant ratio (c / a) of the nano barium titanate microcrystals are all around 1.0000, and in the XRD diagram, the diffraction peak between 44 ° and 46 ° of the 2θ angle appears as a single peak without significant splitting, , which means that the nano barium titanate microcrystals are standard cubic phase, the development is more complete, and the crystalline form is better; All of the barium-titanium ratios (Ba/Ti ratios) are around 1, meaning that the nano-barium titanate microcrystals have very high purity.

The present invention further provides a method for producing barium titanate powder,

First, according to the above-described manufacturing method, manufacturing nano-barium titanate microcrystals;

At 200 to 1300 ℃, but calcined to nano barium titanate microcrystals, when the calcination time is 1 to 10 hours, comprising the step of obtaining barium titanate powder.

In the present invention, using nano barium titanate microcrystals as a raw material and performing high-temperature calcination thereon, barium titanate powder having a small particle size and uniformity, high purity, excellent dispersibility, and excellent crystalline growth can be obtained. have.

Specifically, the particle size of the barium titanate powder is closely related to the firing temperature. According to the inventor's study, the growth of crystal grains by low-temperature calcination at less than 500 DEG C is not remarkable; Barium titanate crystal grains gradually increase by high-temperature calcination at 500 to 1300°C, and as the calcination temperature rises, the increase in crystal grains becomes more remarkable. can

In addition, the calcination temperature is 1100 ° C. or less, and as the calcination temperature rises, the degree of crystallization of the barium titanate powder gradually improves, but if the calcination temperature is too high, for example, higher than 1100 ° C. In general, the firing temperature is controlled to 200~1100℃, additionally 300~1300℃.

The present invention further provides barium titanate powder, which is manufactured using the above-described manufacturing method. Specifically, the nano-barium titanate microcrystals described above are used as a raw material, and are obtained through high-temperature sintering.

The barium titanate powder has a smaller particle size, uniform particle size distribution, and excellent dispersibility, while the barium titanate powder also has excellent crystal grain growth and high purity characteristics, so that in the electrical ceramic industry It can satisfy the demand for high-quality barium titanate products.

The method for producing nano barium titanate microcrystals provided in the present invention is based on an atmospheric pressure hydrothermal synthesis process using a high-concentration aqueous nano-titanium dioxide dispersion as a titanium source. Barium titanate microcrystals are prepared. In particular, through rational selection of reaction raw materials and control of atmospheric pressure hydrothermal synthesis reaction conditions, nano-barium titanate microcrystals having an average particle diameter of less than 50 nm, or even 10 to 20 nm, can be obtained, and the cubic phase or mostly cubic phase to be. By using the nano-barium titanate microcrystals obtained using the above manufacturing method as a raw material and performing additional calcination or other processing, barium titanate powder having a desired particle size can be obtained, and the barium titanate powder has very high purity and crystallinity. , and excellent dispersibility, and can satisfy the demand for barium titanate in the electric ceramic industry.

At the same time, since the synthesis of nano barium titanate microcrystals is carried out under normal pressure and does not require high temperature, it not only ensures production safety, reduces production energy consumption and equipment cost, but also continuously produces nano barium titanate microcrystals or barium titanate powder and improve production efficiency. In addition, since the mass concentration of the aqueous nano titanium dioxide dispersion used is 20% or more, the production efficiency is further improved.

The nano barium titanate microcrystals provided in the present invention have a small particle size, a narrow distribution section, high purity, and excellent dispersibility. Barium powder can be produced, and the barium titanate powder has very high purity, crystallinity, and excellent dispersibility, so that the demand for barium titanate in the electrical ceramic industry can be satisfied.

The present invention provides a method for producing nano barium titanate microcrystals.

The present invention provides nano barium titanate microcrystals, characterized in that produced by the above-described method for producing nano barium titanate microcrystals.

The present invention provides a method for producing barium titanate powder comprising the step of preparing nano barium titanate microcrystals using the above-described method for producing nano barium titanate microcrystals.

The method for producing barium titanate powder provided in the present invention can obtain barium titanate powder with high purity and excellent dispersibility by using the above-described nano barium titanate microcrystals as a raw material, and through simple high-temperature firing, and also barium titanate powder As it achieves excellent growth of crystal grains and effective control of grain size in the high-temperature calcination process, it is possible to satisfy the demand for barium titanate in the electric ceramic industry.

In addition, the manufacturing method of the barium titanate powder has a simple process and reliable characteristics, and is suitable for industrial lot production.

The barium titanate powder provided by the present invention has high purity, high dispersibility, excellent crystal grain growth, and controllable particle size, so it can satisfy the demand for high quality barium titanate in the electric ceramic industry. can

1 is a particle size distribution curve measured after nano titanium dioxide used in Examples 1-5 of the present invention is dispersed in deionized water at a mass concentration of 1%.
2 is a particle size distribution curve measured after nano titanium dioxide used in Examples 1-5 of the present invention is dispersed in deionized water at a mass concentration of 10%.
3 is a particle size distribution curve measured after nano titanium dioxide used in Examples 1-5 of the present invention is dispersed in deionized water at a mass concentration of 50%.
4 is an XRD pattern of nano barium titanate microcrystals prepared in Example 1 of the present invention.
5 is an XRD pattern of nano barium titanate microcrystals prepared in Example 3 of the present invention.
6 is an XRD pattern of nano barium titanate microcrystals prepared in Example 4 of the present invention.
7 is an XRD pattern of nano barium titanate microcrystals prepared in Example 5 of the present invention.
8 is an XRD pattern of nano barium titanate microcrystals prepared in Example 6 of the present invention.
9 is an XRD pattern of nano barium titanate microcrystals prepared in Example 7 of the present invention.
10 is a TEM image of nano barium titanate microcrystals prepared in Example 2 of the present invention.
11 is a TEM image of the barium titanate powder prepared in Example 8 of the present invention.
12 is a TEM image of the barium titanate powder prepared in Example 9 of the present invention.
13 is a SEM image of the barium titanate powder prepared in Example 10 of the present invention.
14 is a SEM image of the barium titanate powder prepared in Example 11 of the present invention.
15 is a SEM image of the barium titanate powder prepared in Example 12 of the present invention.
16 is an XRD pattern of nano barium titanate microcrystals prepared in Example 2 of the present invention and barium titanate powder prepared in Examples 8-13.
FIG. 17 is a partially enlarged view of FIG. 16 .
18 is an XRD pattern of barium titanate microcrystals prepared in Comparative Example 1 of the present invention.
19 is an XRD pattern of barium titanate microcrystals prepared in Comparative Example 2 of the present invention.

In order to make the object, technical solution and advantage of the embodiment of the present invention more clear, the following clearly and completely describes the technical solution according to the embodiment of the present invention in conjunction with the accompanying drawings according to the embodiment of the present invention, It is obvious that the described embodiments are only partial embodiments of the present invention and not all embodiments. Based on the embodiment according to the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

In the present invention, the characteristics of nano barium titanate microcrystals and barium titanate powder are shown using the following detection techniques or means.

(1) The surface shape of the sample is observed using a scanning electron microscope and a projection electron microscope, and the average particle diameter of the barium titanate primary particles is obtained by statistics about the particle diameter of about 200 particles.

(2) Using an X-ray diffractometer (D8 Advance), collect X-ray diffraction patterns within the range of 20-80 with parameters of 0.02° step length and 2s integration time, and Rietveld method with Topas software. Calculate the lattice constant ratio (c/a) by performing structural repair using

(3) Analyze the specific surface area of the material using the BET method.

(4) Measure the barium-titanium ratio of the barium titanate powder by using ICP-MS analysis.

Example 1

At room temperature, the nano titanium dioxide powder is uniformly distributed in deionized water and slowly stirred until uniformly mixed to prepare 100 g of an aqueous dispersion of nano titanium dioxide having a mass concentration of 48%.

Under atmospheric nitrogen gas atmosphere protection, 355 g of Ba(OH) ₂ .8H ₂ O and 150 mL deionized water were added to a three-necked round bottom flask, and heated and stirred at 100° C. until barium hydroxide was completely dissolved.

The nano titanium dioxide aqueous dispersion was rapidly added to the three-necked round-bottom flask, and the heating power for the existing three-necked round-bottom flask was maintained during the addition process, and the temperature measured for the obtained mixing system was 97±2 ℃, the temperature is raised to 100 ℃ with continuous stirring, and the reflux reaction proceeds for 5 h. After completion of the reaction, the reaction product was taken out, filtered, washed, and dried to obtain nano barium titanate microcrystals.

The nano titanium dioxide powder used in this example has a volume basis D50≤10 nm, and the particle size distribution curves measured by dispersing the nano titanium dioxide powder in deionized water at concentrations of 1%, 10% and 50% are respectively As shown in FIGS. 1, 2 and 3 .

Example 2-3

In Example 2-3, other manipulation steps were consistent with Example 1, and the reflux reaction time was changed to 10 h and 20 h, respectively, and only in that nano-barium titanate microcrystals were obtained.

Example 4

Without changing the deionized water volume, reducing the mass of titanium dioxide and barium hydroxide by half, respectively, adding 51 g of sodium hydroxide, and carrying out other operation steps the same as in Example 2, to obtain nano barium titanate microcrystals did

Example 5

Maintaining the mass concentration of the aqueous nano titanium dioxide dispersion at 48%, reducing the mass of the aqueous nano titanium dioxide dispersion to half the original, that is, 50 g, changing the molar ratio of titanium dioxide and barium hydroxide, and other operation steps are carried out In the same manner as in Example 2, nano barium titanate microcrystals were obtained.

Example 6-7

The manufacturing process of Example 6-7 is basically the same as that of Example 2, except that the median particle diameter D50 calculated based on the volume of nano titanium dioxide in Example 6 was about 17 nm; It is differentiated in that the median particle diameter D50 calculated based on the volume of nano titanium dioxide in Example 7 is about 29 nm.

The reaction conditions in Examples 1-7 described above may be specifically referred to Table 1, and the product of the synthesized nano barium titanate microcrystals may be referred to Table 2.

Example Barium hydroxide aqueous solution Nano titanium dioxide aqueous dispersion reaction conditions amount of substance
(mol) solvent volume
(mL) Temperature
(℃) amount of substance
(mol) mass concentration
(%) D50
(nm) Temperature
(℃) hour
(h) One 1.125 150 100 0.6 48 ≤10 100 5 2 1.125 150 100 0.6 48 ≤10 100 10 3 1.125 150 100 0.6 48 ≤10 100 20 4 0.563 150 100 0.3 24 ≤10 100 10 5 1.125 150 100 0.3 48 ≤10 100 10 6 1.125 150 100 0.6 48 17 100 10 7 1.125 150 100 0.6 48 29 100 10

Example Average particle size (nm) BET specific surface area
(m ² /g) Lattice Constant Ratio
(c/a) Barium Titanium Ratio Raman Peak Ratio
(305cm ^-1 /183cm ^-1 ) One 14 74 1.0000 0.990 0.90 2 15 71 1.0000 0.993 0.86 3 12 79 1.0000 0.998 0.88 4 13 75 1.0000 1.001 0.85 5 16 69 1.0000 1.000 0.86 6 31 26 1.0041 0.992 0.87 7 50 14 1.0056 0.998 0.86

4 is an X-ray diffraction (XRD) pattern of nano-barium titanate microcrystals obtained in Example 1, and FIGS. 5, 6, 7, 8 and 9 are nano-titanic acids obtained in Examples 3-7, respectively. It is an XRD pattern of barium microcrystals, and the XRD pattern in Example 2 is similar to that of FIG. 4 . Referring to the XRD pattern described above, in the 2θ angle of the nano barium titanate microcrystals obtained in Examples 1-7, a diffraction peak between 44° and 46° appears as one single peak, and significant cracking does not occur. , which means that the grid development is better.

Referring to the lattice constant ratio (c / a) according to Table 2, the lattice constant ratio (c / a) of the nano barium titanate microcrystals prepared in Examples 1-7 is 1.0000 left and right, confirming that it is a typical cubic phase. have.

Referring to the Ba/Ti ratio data in Table 2, in the nano-barium titanate microcrystals obtained in Examples 1-7, the Ba/Ti ratio is all near 1, and most of them are concentrated between 0.990 and 1.001. It can be seen that the nano barium titanate microcrystals have a very high purity.

FIG. 10 is a projection electron microscope (TEM) image of nano barium titanate microcrystals obtained in Example 2, which is similar to the shape of nano barium titanate microcrystals according to Example 1. FIG. Referring to FIGS. 1 and 2 together, the average particle diameter of the nano barium titanate microcrystals prepared in Example 1-2 is all 15 nm left and right, excellent dispersibility, no significant agglomeration, and more uniform particle diameter do; All primary particles of the nano-barium titanate microcrystals according to Examples 3-7 had an average particle diameter of 50 nm or less.

Examples 8-13

The nano barium titanate microcrystals obtained in Example 2 were calcined for about 3 h in a muffle furnace to obtain barium titanate powder, wherein the calcination temperature according to Examples 8-13 was 300 ° C., 500 ° C., 700 ° C., respectively. 900°C, 1100°C, and 1300°C. Specific firing process and product shape can be specifically referred to Table 3.

firing process product shape Example Temperature
(℃) hour
(h) average particle size
(nm) BET specific surface area
(m ² /g) Lattice Constant Ratio
(c/a) Barium Titanium Ratio Raman peak ratio (305cm ^-1 / 183cm ^-1) 8 300 3 18 58 1.0000 0.999 0.80 9 500 3 19 49 1.0021 1.000 0.83 10 700 3 52 13 1.0040 0.994 0.88 11 900 3 65 10 1.0053 1.001 1.11 12 1100 3 200 3 1.0067 0.998 1.18 13 1300 3 303 2 1.0081 1.001 1.53

11 and 12 are TEM images of barium titanate powder obtained in Examples 8-9, respectively. 11-12 and Table 3, it can be seen that the particle dispersion of the barium titanate powder obtained in Examples 8-9 is excellent, and no significant agglomeration is observed. The average particle diameter of the primary particles is both left and right of 20 nm, and from this, it can be seen that the growth of crystal grains due to low-temperature calcination proceeding at 300°C to 500°C is not remarkable.

13, 14 and 15 are scanning electron microscope (SEM) images of barium titanate powder in Examples 10-12, respectively. 13-15 and Table 3, when the sintering temperature is increased from 500 ℃ to 1300 ℃, the barium titanate crystal grains gradually increase, and it can be seen that the particle size increases from about 20 nm to 200 nm left and right, It means that crystal grains become significantly larger by high-temperature calcination at 500°C to 1300°C.

16 is an XRD pattern of nano barium titanate microcrystals prepared in Example 2 of the present invention and barium titanate powder prepared in Examples 8-13, and FIG. 17 is a diffraction peak position with a 2θ angle of 45° in FIG. is an enlarged view. 16 and 17 , the nano barium titanate microcrystals undergo calcination, and the crystal growth is more excellent, and as the calcination temperature rises, the degree of crystallization of the barium titanate powder gradually becomes excellent, and in particular, the calcination temperature increases When the temperature is 300 ° C. to 1100 ° C. (Example 8-12), the diffraction peak in the vicinity of 45 ° does not cause significant cracking in the 2θ angle, appears as one single peak, and the firing temperature is 1300 ° C. (Example 13) When , it can be seen that the diffraction peak at 45° is cracked.

Referring to the measurement results in Table 4, the growth of crystal grains due to low-temperature calcination at 300°C to 500°C is not remarkable, but when the calcination temperature rises from 500°C to 1300°C, the barium titanate crystal grains gradually It can be seen that the grain size increases from 20 nm to 300 nm left and right, and it means that the crystal grains are remarkably increased by high-temperature firing at 500° C. to 1300° C.

Comparative Example 1

The manufacturing process of Comparative Example 1 is basically the same as in Example 2, and when mixing the mixing system, the aqueous titanium dioxide dispersion is slowly added to a three-necked round bottom flask containing an aqueous barium hydroxide solution, but stirred and mixed at high speed while adding , it is differentiated only in that the temperature of the entire mixing system is basically maintained at 100°C to make it constant.

The specific physical property test results of the nano barium titanate microcrystals may be referred to Table 4, and the XRD pattern thereof is as shown in FIG. 18 .

Comparative Example 2

The manufacturing process of Comparative Example 2 is basically the same as that of Example 2, and when mixing the mixed system, the mass of the nano titanium dioxide powder is not changed, but it is differentiated only in that the mass concentration of the nano titanium dioxide is 8%.

The specific physical property test results of the nano barium titanate microcrystals can be referred to Table 4, and the XRD pattern thereof is as shown in FIG. 19 .

18 and 19 , in Comparative Example 1-2, nano-barium titanate fines with better growth of crystal grains likewise through the method of slowly adding the aqueous nano-titanium dioxide dispersion or reducing the concentration of the aqueous nano-titanium dioxide dispersion You know you can get a decision.

However, if the test results of Comparative Example 1-2 and Example 2 are compared, when the aqueous titanium dioxide dispersion is slowly added to keep the mixing system basically constant, or when a low concentration nano titanium dioxide aqueous dispersion is used, the obtained nano The average grain size of the barium titanate microcrystals all increase. On the other hand, if the concentration of the nano titanium dioxide aqueous dispersion is lowered, the production efficiency of nano barium titanate microcrystals is also significantly reduced.

comparative example Average particle size (nm) BET specific surface area
(m ² /g) Lattice Constant Ratio
(c/a) Barium Titanium Ratio Raman Peak Ratio
(305cm ^-1 /183cm ^-1 ) One 20 60 1.0000 0.994 0.87 2 21 58 1.0000 0.991 0.86

Finally, each of the above embodiments is only for explaining the technical solution of the present invention, and is not limited thereto. Although the present invention has been described in detail with reference to each of the above-described embodiments, those skilled in the art may still modify the technical solutions described in each of the above-described embodiments, or some or all technical features thereof Equivalent substitution can be made, and it can be understood that the essence of the related technical solution does not deviate from the scope of the technical solution of each embodiment of the present invention by such modification or substitution.

Claims (10)

By rapidly mixing the nano titanium dioxide aqueous dispersion having a lower temperature and an aqueous solution of barium hydroxide having a higher temperature, the temperature of the obtained mixing system is at least 2 ° C lower than the temperature of the aqueous barium hydroxide solution by rapid mixing of both. but; Here, the mass concentration of the nano titanium dioxide aqueous dispersion is 20% or more; and
Nano barium titanate microcrystals, characterized in that it comprises the step of obtaining nano barium titanate microcrystals by allowing the mixed system to react hydrothermal synthesis at atmospheric pressure at 90 to 110 ° C in an inert atmosphere, collecting the reaction product, washing and drying manufacturing method.
According to claim 1,
The method for producing nano barium titanate microcrystals, characterized in that the aqueous dispersion of nano titanium dioxide having a lower temperature is added to an aqueous solution of barium hydroxide having a higher temperature and rapidly mixed to obtain the mixed system.
According to claim 1,
the temperature of the nano-titanium dioxide aqueous dispersion does not exceed 50°C; During rapid mixing, the method for producing nano-barium titanate microcrystals, characterized in that the temperature of the aqueous solution of barium hydroxide is controlled to 70° C. or higher.
According to claim 1,
In the aqueous dispersion of nano titanium dioxide, the method for producing nano barium titanate microcrystals, characterized in that the median particle size calculated based on the volume of the nano titanium dioxide does not exceed 30 nm.
According to claim 1,
In the mixed system, the molar ratio between Ba ions and Ti atoms is 1 to 4 : Method for producing nano barium titanate microcrystals, characterized in that 1.
According to claim 1,
The mass concentration of the aqueous barium hydroxide solution is 20% or more, A method for producing nano-barium titanate microcrystals.
According to claim 1,
The method for producing nano barium titanate microcrystals, characterized in that the time of the atmospheric pressure hydrothermal synthesis reaction is 30 minutes or more.
8. Nano barium titanate microcrystals, characterized in that produced by the method for producing nano barium titanate microcrystals according to any one of claims 1 to 7.
Using the method for producing nano-barium titanate microcrystals according to any one of claims 1 to 7, comprising: preparing nano barium titanate microcrystals; and
The method for producing barium titanate powder, comprising the step of obtaining a barium titanate powder by calcining the nano-barium titanate microcrystals at 200 to 1300°C.
10. Barium titanate powder, characterized in that it is produced using the method for producing barium titanate powder according to claim 9.

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