阅读说明：本技术 纳米氧化锆粉体、其制备方法及所得分散液、光学膜 (Nano zirconium oxide powder, preparation method thereof, dispersion liquid obtained by preparation method and optical film ) 是由 宋锡滨 张栋 奚洪亮 艾辽东 朱恒 于 2020-11-23 设计创作，主要内容包括：本发明提出一种纳米氧化锆粉体、其制备方法及所得分散液、光学膜,属于精细化工领域,可解决现有的纳米氧化锆颗粒及其制备方法无法满足透明有机无机复合物高性能需求的技术问题。本发明提供了一种纳米氧化锆粉体,所述纳米氧化锆粉体的粒径为3-10nm,比表面积为200-240m~2/g,所述纳米氧化锆粉体为四方相晶粒结构,且四方相晶粒结构的比例占粉体的60-95％。本发明所得纳米氧化锆粉体具有粒径小、比表面积大、粒子单分散效果好、主晶相为四方相等特点,于水中分散后所得的水分散液在后续例如制备增亮膜或防反射膜中能够大幅提升高折射涂层的折射率,提升膜的性能。(The invention provides a nano zirconia powder, a preparation method thereof, a dispersion liquid and an optical film, belongs to the field of fine chemical engineering, and can solve the technical problem that the high-performance requirements of transparent organic-inorganic composites cannot be met by the existing nano zirconia particles and the preparation method thereof. The invention provides nano zirconia powder, the particle diameter of the nano zirconia powder is 3-10nm, the specific surface area is 200- 2 The nano zirconia powder is of a tetragonal crystal grain structure, and the proportion of the tetragonal crystal grain structure accounts for 60-95% of the powder. The nanometer zirconia obtained by the inventionThe powder has the characteristics of small particle size, large specific surface area, good particle monodispersion effect, tetragonal main crystal phase and the like, and the aqueous dispersion obtained after dispersion in water can greatly improve the refractive index of a refraction coating in subsequent preparation of a brightness enhancement film or an anti-reflection film and improve the performance of the film.)

1. The nano zirconia powder is characterized in that the particle diameter of the nano zirconia powder is 3-10nm, the specific surface area is 200-240m²The nano zirconia powder is of a tetragonal crystal grain structure, and the proportion of the tetragonal crystal grain structure accounts for 60-95% of the powder.

2. The method for preparing the nano zirconia powder according to claim 1, comprising the following steps:

dissolving zirconium salt and stable element salt in water together to obtain a solution A;

dissolving alkali in water to obtain a solution B;

fully mixing the solution A and the solution B under stirring to generate a precipitate, wherein the mass of the precipitate accounts for 1-40% of the mass of the total mixed solution; washing and filtering the precipitate for multiple times to obtain a precursor C;

adding water and organic acid or salt thereof into the precursor C for pulping, wherein the total solid content in the obtained pulp is 6-20 wt%;

putting the obtained slurry into a reaction kettle, wherein the filling amount is 60-90%, carrying out hydrothermal reaction at 180-220 ℃ for 1-12h, and obtaining reaction liquid after the reaction;

and directly drying the reaction solution or concentrating, washing and drying to obtain the nano zirconia powder.

3. The method according to claim 2, wherein the added zirconium salt is a water-soluble zirconium salt selected from at least one of basic carbonate, nitrate, acetate, chloride, oxychloride; the added stable element salt is chloride or nitrate of stable element, wherein the stable element is at least one of aluminum, magnesium, titanium and rare earth elements; the alkali is at least one of ammonia water, sodium hydroxide, potassium hydroxide and lithium hydroxide.

4. The method according to claim 3, wherein the concentration of the added zirconium salt is 2mol/L or less, the molar concentration ratio of the added stabilizing element to the zirconium element is 2/98 to 30/70, and the concentration of the added alkali is 8mol/L or less.

5. The preparation method according to claim 2, wherein the organic acid is at least one selected from the group consisting of a monocarboxylic acid, a polycarboxylic acid and a hydroxycarboxylic acid, wherein the monocarboxylic acid is at least one selected from the group consisting of formic acid, acetic acid, propionic acid and butyric acid, the polycarboxylic acid is at least one selected from the group consisting of oxalic acid, malonic acid, succinic acid and phthalic acid, and the hydroxycarboxylic acid is at least one selected from the group consisting of lactic acid, malic acid, tartaric acid and citric acid; the salt of the organic acid is alkali metal salt thereof, and is selected from potassium salt or sodium salt.

6. The method according to claim 5, wherein the organic acid or a salt thereof is added in an amount of 10 to 100% based on the molar concentration of the sum of the zirconium element and the stabilizing element.

7. The preparation method according to claim 2, wherein when the boiling point of the added organic acid is less than 150 ℃, the reaction solution is directly dried to obtain nano zirconia powder; when the boiling point of the added organic acid is higher than 150 ℃, the reaction solution is concentrated, washed and dried for many times to obtain the nano zirconium oxide powder.

8. The method according to claim 7, wherein the drying means is selected from any one of vacuum low-temperature drying, drying and spraying, and the concentration washing means is selected from any one of ultrafiltration, rotary evaporation and ceramic membrane concentration washing.

9. The dispersion liquid containing the nano zirconia powder of claim 1, wherein the refractive index of the dispersion liquid is 1.343 to 1.472, the dispersion liquid has a positive Zeta potential value under the condition that the pH is less than or equal to 7, and the content of the nano zirconia in the dispersion liquid is 5 to 60 wt%.

10. The dispersion according to claim 9, wherein the dispersion has a Zeta potential value in the range of 0 to 60mv at pH 7 or less.

11. The dispersion according to claim 9 or 10, wherein the dispersion is obtained by concentrating and washing the reaction solution obtained in the production process according to the production method of claim 2 to remove the organic acid or the salt thereof, or by dispersing the nano-zirconia powder obtained in the production method of claim 2 in water.

12. An optical film, characterized by being prepared from the dispersion liquid containing nano zirconia powder according to any one of claims 9 to 11.

13. Use of the nano zirconia powder according to claim 1 or the dispersion comprising the nano zirconia powder according to any one of claims 9 to 11 in the preparation of an optical film.

Technical Field

The invention belongs to the field of fine chemical engineering, and particularly relates to nano zirconia powder, a preparation method thereof, and a dispersion liquid and an optical film obtained by the preparation method.

Background

In recent years, zirconia particle dispersions have been used in optical applications by combining them with transparent resins or films and utilizing their high refractive index. For example, optical films such as brightness enhancement films and anti-reflection films prepared from the high-refraction zirconium oxide dispersion can be used on LCD displays to increase the brightness and definition of screens; the refractive index of the LED sealing resin can be improved, light emitted by the light emitting body can be more effectively obtained, and the brightness of the LED can be improved. In conclusion, its high refractive properties can be used in high refractive coatings, which find applications in different fields.

The refractive index of the zirconia dispersion liquid is closely related to the particle size, the crystal structure, the particle dispersion state and the dispersion liquid preparation process of the nano zirconia in the system. CN201810704465.3 discloses a method for preparing highly dispersed nano zirconia particles and transparent dispersoid thereof, which adopts a method of pyrolyzing inorganic zirconium salt under a supergravity environment to directly prepare nano zirconia particles, and the agglomeration is greatly reduced along with the improvement of supergravity level, and then the nano zirconia particles are directly transparent zirconia liquid phase dispersoid after being washed and modified. The zirconia prepared by the method has small particle size and good dispersibility, but the crystal structure of the powder is a monoclinic phase, the refractive index of the powder is far lower than that of tetragonal phase powder, and the refractive index of the corresponding liquid phase dispersoid is also lower under the same condition. Therefore, how to prepare the nano zirconia particles with excellent performance and the zirconia dispersion liquid with stable system, uniform dispersion and high refractive index are very important for better meeting the performance requirements of the transparent organic-inorganic composite.

Disclosure of Invention

The invention provides nano zirconia powder, a preparation method thereof, a dispersion liquid and an optical film, wherein the nano zirconia powder has the characteristics of small particle size, large specific surface area, good particle monodispersion effect, tetragonal main crystal phase and the like, and the water dispersion liquid has the characteristics of uniform dispersion, high refractive index and the like after being dispersed in water.

In order to achieve the above purpose, the invention provides a nano zirconia powder, the particle diameter of the nano zirconia powder is 3-10nm, the specific surface area is 200-²The nano zirconia powder is of a tetragonal crystal grain structure, and the proportion of the tetragonal crystal grain structure accounts for 60-95% of the powder.

The invention also provides a preparation method of the nano zirconia powder according to the technical scheme, which comprises the following steps:

dissolving zirconium salt and stable element salt in water together to obtain a solution A;

dissolving alkali in water to obtain a solution B;

fully mixing the solution A and the solution B under stirring to generate a precipitate, wherein the mass of the precipitate accounts for 1-40% of the mass of the total mixed solution; washing and filtering the precipitate for multiple times to obtain a precursor C;

adding water and organic acid or salt thereof into the precursor C for pulping, wherein the total solid content in the obtained pulp is 6-20 wt%;

putting the obtained slurry into a reaction kettle, wherein the filling amount is 60-90%, carrying out hydrothermal reaction at 180-220 ℃ for 1-12h, and obtaining reaction liquid after the reaction;

and directly drying the reaction solution or concentrating, washing and drying to obtain the nano zirconia powder.

Preferably, the added zirconium salt is water-soluble zirconium salt, and is selected from at least one of basic carbonate, nitrate, acetate, chloride and oxychloride; the added stable element salt is chloride or nitrate of stable element, wherein the stable element is at least one of aluminum, magnesium, titanium and rare earth elements; the alkali is at least one of ammonia water, sodium hydroxide, potassium hydroxide and lithium hydroxide.

Preferably, the concentration of the added zirconium salt is less than or equal to 2mol/L, the molar concentration ratio of the added stability element to the zirconium element is 2/98-30/70, and the concentration of the added alkali is less than or equal to 8 mol/L.

Preferably, the organic acid is selected from at least one of monocarboxylic acid, polycarboxylic acid and hydroxycarboxylic acid, wherein the monocarboxylic acid is selected from at least one of formic acid, acetic acid, propionic acid and butyric acid, the polycarboxylic acid is selected from at least one of oxalic acid, malonic acid, succinic acid and phthalic acid, and the hydroxycarboxylic acid is selected from at least one of lactic acid, malic acid, tartaric acid and citric acid; the salt of the organic acid is alkali metal salt thereof, and is selected from potassium salt or sodium salt.

Preferably, the organic acid or its salt is added in an amount of 10 to 100% of the molar concentration of the sum of the zirconium element and the stabilizing element.

Preferably, when the boiling point of the added organic acid is less than 150 ℃, the reaction liquid is directly dried to obtain nano zirconium oxide powder; when the boiling point of the added organic acid is higher than 150 ℃, the reaction solution is concentrated, washed and dried for many times to obtain the nano zirconium oxide powder.

Preferably, the drying mode is selected from any one of vacuum low-temperature drying, drying and spraying, and the concentration washing mode is selected from any one of ultrafiltration, rotary evaporation and ceramic membrane concentration washing.

The invention also provides a dispersion liquid containing the nano zirconia powder in the technical scheme, the refractive index of the dispersion liquid is 1.343-1.472, the dispersion liquid has a positive Zeta potential value under the condition that the pH value is less than or equal to 7, and the content of the nano zirconia in the dispersion liquid is 5-60 wt%.

Preferably, the Zeta potential value of the dispersion liquid is 0-60 mv under the condition that the pH value of the dispersion liquid is less than or equal to 7 and the pH value of the dispersion liquid is less than or equal to 7.

Preferably, the dispersion liquid is obtained by concentrating and washing the reaction liquid obtained in the preparation process by the preparation method described in the above technical scheme to remove organic acid or salt thereof, or is obtained by dispersing the nano zirconia powder obtained in the above technical scheme in water.

The invention also provides an optical film which is prepared by adopting the dispersion liquid containing the nano zirconia powder in any one of the technical schemes.

The invention also provides application of the nano zirconia powder according to the technical scheme or the dispersion liquid containing the nano zirconia powder according to any one of the technical schemes in preparation of an optical film.

Compared with the prior art, the invention has the advantages and positive effects that:

1. the nano zirconia powder provided by the invention has the characteristics of small particle size, large specific surface area, good particle monodispersion effect, tetragonal main crystal phase and the like;

2. the dispersion liquid prepared by the obtained nano zirconia powder has the advantages of stable system, uniform dispersion, high refractive index and the like, the refractive index of the dispersion liquid can reach 1.343-1.472, and the dispersion liquid has a larger positive Zeta potential value under the condition that the pH value is less than or equal to 7;

3. the dispersion liquid with the characteristics can greatly improve the refractive index of a refractive coating layer in the subsequent preparation of a brightness enhancement film or an anti-reflection film, and the performance of the film is improved.

Drawings

FIG. 1 is a transmission electron microscope image of a nano zirconia powder provided in example 1 of the present invention;

fig. 2 is an XRD of the nano zirconia powder provided in embodiment 1 of the present invention;

fig. 3 is a distribution diagram of the particle size of the nano zirconia powder provided in embodiment 1 of the present invention;

FIG. 4 is a transmission electron microscope image of the nano zirconia powder provided by comparative example 1 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention providesNano zirconium oxide powder, the grain diameter of the nano zirconium oxide powder is 3-10nm, the specific surface area is 200-240m²The nano zirconia powder is of a tetragonal crystal grain structure, and the proportion of the tetragonal crystal grain structure accounts for 60-95% of the powder.

In the above embodiment, the particle size, specific surface area and tetragonal crystal structure ratio of the nano zirconia powder are defined, and the synergistic effect of the three components can make the obtained nano zirconia powder have the characteristics of uniform dispersion, high refractive index and the like after dispersion, specifically, when the particle size is small and the specific surface is large, the particle dispersibility is good, the prepared aqueous dispersion liquid can be uniformly dispersed, and the refractive index is higher; and when the zirconia crystal phase is a tetragonal phase and the proportion of the tetragonal phase is higher, the corresponding refractive index is higher (the refractive index of the zirconia of the tetragonal phase is 2.40, which is obviously higher than the refractive index of the zirconia of the monoclinic phase of 2.02). It is understood that the particle size of the nano zirconia powder may be 4, 5, 6, 7, 8, 9nm or any value within the above range, and the specific surface area may be 205, 210, 215, 220, 225, 230, 235m²The proportion of the tetragonal phase grain structure in the powder can be 65, 70, 75, 80, 85, 90% or any value in the range.

The embodiment of the invention also provides a preparation method of the nano zirconia powder according to the embodiment, which comprises the following steps:

dissolving zirconium salt and stable element salt in water together to obtain a solution A;

dissolving alkali in water to obtain a solution B;

fully mixing the solution A and the solution B under stirring to generate a precipitate, wherein the mass of the precipitate accounts for 1-40% of the mass of the total mixed solution; washing and filtering the precipitate for multiple times to obtain a precursor C;

adding water and organic acid or salt thereof into the precursor C for pulping, wherein the total solid content in the obtained pulp is 6-20 wt%;

putting the obtained slurry into a reaction kettle, wherein the filling amount is 60-90%, carrying out hydrothermal reaction at 180-220 ℃ for 1-12h, and obtaining reaction liquid after the reaction;

and directly drying the reaction solution or concentrating, washing and drying to obtain the nano zirconia powder.

In the preparation method of the nano zirconia powder defined in the above embodiment, one of the key points lies in the adding sequence of the organic acid or the salt thereof, that is, the organic acid or the salt thereof needs to be introduced before pulping rather than after pulping, because the viscosity of the precursor is greatly reduced in the pulping process due to the effect of charges before pulping, so that the pulping dispersion effect can be improved, the concentration of the precursor in a kettle can be improved, and the defects that the pulping dispersion effect is poor, the prepared powder has a high particle size, is agglomerated, is not easy to disperse and the like are avoided. The second critical point is the hydrothermal reaction temperature, which is reported in the prior art to be 170 ℃ or higher, and the temperature in this example is limited to 180-220 ℃, for example, 190, 195, 200, 205, 210, 215 ℃ or any value in the above range, although intersecting with the existing range, the temperature has its specific technical effect. The temperature of the hydrothermal reaction in the invention directly affects the grain structure of the obtained powder, i.e. if < 180 ℃, for example 170 ℃, the crystal form of the obtained powder is a monoclinic phase grain structure rather than the expected tetragonal phase grain structure; and if the temperature is higher than 220 ℃, the production equipment is strictly required, and the scale-up production is not facilitated.

In a preferred embodiment, the added zirconium salt is a water-soluble zirconium salt selected from at least one of basic carbonate, nitrate, acetate, chloride and oxychloride; the added stable element salt is chloride or nitrate of stable element, wherein the stable element is at least one of aluminum, magnesium, titanium and rare earth elements; the alkali is at least one of ammonia water, sodium hydroxide, potassium hydroxide and lithium hydroxide.

In a preferred embodiment, the concentration of the added zirconium salt is less than or equal to 2mol/L, the molar concentration ratio of the added stabilizing element to the zirconium element is 2/98-30/70, and the concentration of the added alkali is less than or equal to 8 mol/L. It is understood that the amount of the above-mentioned stability elements added needs to be strictly controlled, and should not be too much or too little, because too little will tend to result in a powder with a small proportion of tetragonal phase and even a monoclinic phase, and too much will tend to result in a powder with a high content of stability elements and thus will affect the refractive index of the powder.

In a preferred embodiment, the organic acid is selected from at least one of monocarboxylic acid, polycarboxylic acid and hydroxycarboxylic acid, wherein the monocarboxylic acid is selected from at least one of formic acid, acetic acid, propionic acid and butyric acid, the polycarboxylic acid is selected from at least one of oxalic acid, malonic acid, succinic acid and phthalic acid, and the hydroxycarboxylic acid is selected from at least one of lactic acid, malic acid, tartaric acid and citric acid; the salt of the organic acid is alkali metal salt thereof, and is selected from potassium salt or sodium salt.

In a preferred embodiment, the organic acid or its salt is added in an amount of 10 to 100% of the molar concentration of the sum of the zirconium element and the stabilizing element. It is understood that the content of the organic acid and the salt thereof is clearly defined in this example, and is defined as 10 to 100% of the molar concentration of the sum of the zirconium element and the stabilizing element. The reason is that in the prior art (for example, CN200980152342.2), the amount of organic acid added in the preparation of zirconia dispersion is usually 1 time or more of the molar concentration of zirconium, but when the molecular weight of organic acid is large, the addition amount is too large, which causes strong acidity of the reaction slurry and large corrosion to the reaction equipment, and in the later preparation of aqueous dispersion, the solvent-based dispersion needs to be concentrated and washed with a large amount of water for many times, which results in serious water waste, and more importantly, the larger the acid amount, the larger the probability of residual acid amount of the solvent-based dispersion prepared in the later period is, and thus the method is not suitable for industrial production. Therefore, this example limits the amount to the range of 10-100% by optimization of the overall scheme. Preferably, it may be 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or any point in the above range of the molar concentration of the sum of the zirconium element and the stabilizing element.

In a preferred embodiment, when the boiling point of the added organic acid is less than 150 ℃, for example, the reaction solution is directly dried to obtain nano zirconia powder; when the boiling point of the added organic acid is higher than 150 ℃, the reaction solution is concentrated, washed and dried for many times to obtain the nano zirconium oxide powder. It is understood that the organic acid having a boiling point of < 150 ℃ may be selected from, for example, formic acid, acetic acid, propionic acid, etc., and the organic acid having a boiling point of > 150 ℃ may be selected from, for example, oleic acid, citric acid, isovaleric acid, etc., and is merely exemplary and not particularly limited.

In a preferred embodiment, the drying mode is selected from any one of vacuum low-temperature drying, drying and spraying, and the concentration washing mode is selected from any one of ultrafiltration, rotary evaporation and ceramic membrane concentration washing. It is understood that the above-mentioned drying mode and concentration washing mode are all operation modes known to those skilled in the art, and the specific requirements of the specific mode can be selected or adjusted according to actual situations.

The embodiment of the invention also provides a dispersion liquid containing the nano zirconia powder in the embodiment, the refractive index of the dispersion liquid is 1.343-1.472, the dispersion liquid has a positive Zeta potential value of 0-60 mv under the condition that the pH value is less than or equal to 7, and the content of the nano zirconia in the dispersion liquid is 5-60 wt%.

In a preferred embodiment, the Zeta potential value of the dispersion liquid is in the range of 0-60 mv under the condition that the pH value is less than or equal to 7. It is understood that the testing method of the Zeta potential value in this embodiment is as follows: firstly, adding the obtained nano zirconia powder into deionized water, uniformly mixing to prepare a 15 wt% aqueous solution, and then respectively adjusting the pH value by potassium hydroxide to detect to obtain the nano zirconia powder. Wherein the Zeta potential values are measured in the pH2-7 range. It is understood that the nano zirconia content of the dispersion may also be 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 wt% or any point within the above ranges.

In a preferred embodiment, the dispersion is obtained by concentrating and washing the reaction solution obtained in the preparation process by the preparation method described in the above embodiment to remove organic acid or salt thereof, or by dispersing the nano zirconia powder obtained in the above embodiment in water.

The embodiment of the invention also provides an optical film which is prepared by adopting the dispersion liquid containing the nano zirconia powder in any embodiment. It is understood that the optical film provided in the present embodiment may be mainly a brightness enhancement film, an anti-reflection film, and other optical films having a high refractive coating.

Example 1

1.47kg of zirconium oxychloride octahydrate and 138g of yttrium chloride hexahydrate are weighed and dissolved in 8kg of water to obtain a mixed solution A;

421g of sodium hydroxide is dissolved in 6kg of water to obtain a sodium hydroxide solution B;

fully mixing the solution A and the solution B under stirring to generate a precipitate, and washing and filtering the precipitate for multiple times to obtain a precursor C;

adding water and 270g (90% of the molar concentration of the total of the zirconium element and the stabilizing element) of acetic acid into the precursor C, controlling the total volume to be 8L, and stirring and pulping;

putting the obtained slurry into a 10L reaction kettle, and carrying out hydrothermal reaction for 3h at 200 ℃;

and after the reaction is finished, directly drying the reaction solution or drying after concentration and washing to obtain the nano zirconium oxide powder.

The obtained nanometer zirconia powder has particle diameter of 3-10nm and specific surface area of 220m²The nano zirconia powder is of a tetragonal crystal grain structure, and the proportion of the tetragonal crystal grain structure accounts for more than 90% of the powder, as shown in figures 1-3.

Example 2

Weighing 1.47kg of zirconium oxychloride and 69g of yttrium chloride, and dissolving in 8kg of water to obtain a mixed solution A;

dissolving 550g of sodium hydroxide in 6kg of water to obtain a potassium hydroxide solution B;

fully mixing the solution A and the solution B under stirring to generate a precipitate, and washing and filtering the precipitate for multiple times to obtain a precursor C;

adding 160g (56% of the molar concentration of the total of the zirconium element and the stabilizing element) of acetic acid into the precursor C, controlling the total volume to be 8L, and stirring for pulping;

putting the obtained slurry into a 10L reaction kettle, and carrying out hydrothermal reaction for 4h at 180 ℃;

and after the reaction is finished, directly drying the reaction solution or drying after concentration and washing to obtain the nano zirconium oxide powder.

The obtained nano zirconia powder has the grain diameter of3-10nm, specific surface area of 200m²And/g, the nano zirconia powder is of a tetragonal crystal grain structure, and the proportion of the tetragonal crystal grain structure accounts for about 75 percent of the powder.

Example 3

Weighing 1.47kg of zirconium oxychloride and 160g of yttrium chloride, and dissolving in 8kg of water to obtain a mixed solution A;

460g of sodium hydroxide is dissolved in 6kg of water to obtain a sodium hydroxide solution B;

fully mixing the solution A and the solution B under stirring to generate a precipitate, and washing and filtering the precipitate for multiple times to obtain a precursor C;

adding water and 337g (90% of the molar concentration of the total of the zirconium element and the stabilizing element) of propionic acid into the precursor C, controlling the total volume to be 8L, and stirring for pulping;

putting the obtained slurry into a 10L reaction kettle, and carrying out hydrothermal reaction for 3h at 220 ℃;

and after the reaction is finished, directly drying the reaction solution or drying after concentration and washing to obtain the nano zirconium oxide powder.

The obtained nanometer zirconia powder has particle diameter of 3-10nm and specific surface area of 210m²And/g, the nano zirconia powder is of a tetragonal crystal grain structure, and the proportion of the tetragonal crystal grain structure accounts for about 83% of the powder.

Example 4

After the aqueous solution obtained after the hydrothermal reaction in example 1 was concentrated and washed at least 3 times, the organic acid or its salt was removed to obtain an aqueous solution of zirconia at a concentration of 5 wt%, i.e., an aqueous dispersion of nano zirconia.

The concentration of the nano zirconia in the obtained aqueous dispersion is 5 wt%, the refractive index is 1.343, and the Zeta potential value of the obtained dispersion is 55mv under the condition that the pH value is 3.

Example 5

The method for preparing the aqueous dispersion of nano-zirconia was the same as in example 4 except that the solution after hydrothermal reaction in example 2 was used.

The concentration of the nano zirconia in the obtained aqueous dispersion is 30 wt%, the refractive index is 1.386, and the Zeta potential value of the obtained dispersion is 34mv under the condition that the pH value is 5.

Example 6

The method for preparing the aqueous dispersion of nano-zirconia was the same as in example 4 except that the solution after the hydrothermal reaction in example 3 was used.

The concentration of the nano zirconia in the obtained aqueous dispersion is 60 wt%, the refractive index is 1.472, and the Zeta potential value of the obtained dispersion is 25mv under the condition that the pH value is 4.

Comparative example 1

Weighing 1.47kg of zirconium oxychloride and 138g of yttrium chloride, and dissolving in 8kg of water to obtain a mixed solution A;

421g of sodium hydroxide is dissolved in 6kg of water to obtain a sodium hydroxide solution B;

fully mixing the solution A and the solution B under stirring to generate a precipitate, and washing and filtering the precipitate for multiple times to obtain a precursor C;

adding water into the forebody C, stirring and pulping;

putting the obtained slurry into a 10L reaction kettle, adding 270g of acetic acid, controlling the total volume to be 8L, and carrying out hydrothermal reaction at 200 ℃ for 3 h;

and after the reaction is finished, directly drying the reaction solution or drying after concentration and washing to obtain the nano zirconium oxide powder.

As shown in FIG. 4, the obtained nano-zirconia powder had a particle size of about 30nm and a specific surface area of 180m²And/g, the nano zirconia powder is in a tetragonal crystal grain structure.

Comparative example 2

Weighing 1.47kg of zirconium oxychloride and 138g of yttrium chloride, and dissolving in 8kg of water to obtain a mixed solution A;

421g of sodium hydroxide is dissolved in 6kg of water to obtain a sodium hydroxide solution B;

fully mixing the solution A and the solution B under stirring to generate a precipitate, and washing and filtering the precipitate for multiple times to obtain a precursor C;

adding water and 270g of acetic acid into the precursor C, controlling the total volume to be 8L, and stirring and pulping;

putting the obtained slurry into a 10L reaction kettle, and carrying out hydrothermal reaction for 3h at 170 ℃;

and after the reaction is finished, directly drying the reaction solution or drying after concentration and washing to obtain the nano zirconium oxide powder.

The obtained nanometer zirconia powder has an average particle diameter of 30nm and a specific surface area of 177m²And/g, the nano zirconia powder is in a monoclinic phase crystal grain structure.

Comparative example 3

The aqueous dispersion of nano-zirconia was prepared by the same method as in example 4 except that the solution after the hydrothermal reaction in comparative example 1 was used.

The concentration of the nano zirconia in the obtained aqueous dispersion is 5 wt%, the refractive index is relatively low and is 1.334, and the Zeta potential value of the obtained dispersion is 46mv under the condition that the pH value is 3.

Comparative example 4

The aqueous dispersion of nano-zirconia was prepared by the same method as in example 4 except that the solution after the hydrothermal reaction in comparative example 1 was used.

The concentration of the nano zirconia in the obtained aqueous dispersion is 30%, the refractive index of the aqueous dispersion is relatively low, 1.372, and the Zeta potential value of the obtained dispersion is 36mv under the condition that the pH value is 3;

comparative example 5

The aqueous dispersion of nano-zirconia was prepared by the same method as in example 4 except that the solution after hydrothermal reaction in comparative example 2 was used.

The concentration of the nano zirconia in the obtained aqueous dispersion is 60 wt%, the refractive index of the nano zirconia is relatively low and is 1.455, and the Zeta potential value of the obtained dispersion is 23mv under the condition that the pH value of the dispersion is 5;

comparative example 6

The aqueous dispersion of nano-zirconia was prepared by the same method as in example 4 except that the solution after hydrothermal reaction in comparative example 2 was used.

The concentration of the nano zirconia in the obtained aqueous dispersion is 60 wt%, the refractive index is relatively low and is 1.451, and the Zeta potential value of the obtained dispersion is 21mv under the condition that the pH value is 5.

From the above, it can be seen that also at 5 wt%, the refractive index of example 4 is 1.343, the refractive index of comparative example 3 is 1.334, and the difference is 0.009; also at 30 wt%, example 5 had a refractive index of 1.386, and comparative example 4 had a refractive index of 1.372, with a difference of 0.014; also at 60 wt%, the refractive index of example 6 was 1.472, that of comparative example 5 was 1.455, which is a difference of 0.017, and that of comparative example 6 was 1.451, which is a difference of 0.021. This is because the particle size of zirconia in the dispersion in the comparative example was large (comparative examples 3, 4, 5) and the crystal form was a monoclinic phase (comparative example 6), so that the refractive index of the dispersion prepared was relatively low. In addition, although the refractive indexes are not very different from each other in numerical view (0.009-0.021), the difference is inherent in the view of the refractive indexes of the dispersions, for example, when the dispersions with the refractive indexes different from 0.01 are respectively used for preparing a brightness enhancement film for application on a display screen, the light transmittance is 89% and 93%, which is the difference between an A-grade screen and a B-grade screen.