CN101580277A - Crystallized zirconia out phase coating-powder, hollow ball and preparation method thereof - Google Patents

Abstract

The invention relates to crystallized zirconia out phase coating-powder, a hollow ball and a preparation method thereof, in particular to a process for uniformly coating the crystallized zirconia on the surface of a nanometer inorganic oxide particle by the hydro-thermal method and for preparing a crystallized zirconia hollow ball thereby, belonging to the technical field of chemical materials. The invention disperses inorganic oxide powder in a zirconium alkaline solution; and after hydro-thermal treatment, the ferric oxide powder coated by the crystallized zirconia is formed, and the crystallized zirconia hollow ball is prepared thereby. The invention has the advantages of simple technology, low requirement on equipment, easy control of preparation conditions and no need of addition of any organic solvent, the shell thickness of the prepared zirconia can be controlled and regulated by multi-deposit operation, and the original configuration and the thickness of the prepared crystallized zirconia hollow ball thereby can be maintained.

Description

Crystalline zirconia heterogeneously coated powder and hollow sphere and preparation method thereof

technical field

The present invention relates to crystalline zirconia heterogeneously coated powder and hollow spheres and a preparation method thereof. More precisely, the crystalline zirconia is uniformly coated on the surface of nanoscale inorganic oxide particles by a hydrothermal method and obtained by The process for preparing crystalline zirconia hollow spheres belongs to the technical field of chemical materials.

Background technique

Due to the continuous improvement of material preparation requirements, it is often difficult for a single-component powder to meet the environmental requirements in the actual application process. Therefore, designing particles with multiple components and complex microstructures has become a research hotspot in recent years. (F.Caruso. "Nanoengineering of particle surfaces", Adv.Mater.2001, 13, 11-22.) At present, the preparation process of nanoscale coating powder with core-shell structure is mainly limited to the preparation of organic or It is an amorphous coating. However, the physical or chemical properties of these organic or amorphous coatings are not very stable. When used for a long time to resist harsh environments, they are easy to decompose or dissolve, and then separate or peel off from the coated powder. (F.Zhao et al. "Nanocoating Fe ₂ O ₃ Powders with a homogeneous ultrathin ZrO ₂ shell", J.Ceram.Soc.Jpn.2008, 16, 1164-1166) and the coating layer of inorganic crystalline oxide, has Quite stable physical and chemical properties, if the coating in the crystalline state can be achieved, the above problems can be well solved.

The current preparation process of the crystalline zirconia coating layer is to deposit the amorphous zirconia coating layer first, and then heat treatment to crystallize the amorphous coating layer. However, in the process of heat treatment, there will also be problems of cracking and peeling of the amorphous coating. In addition, the coating layer after heat treatment will shrink to a certain extent, and the reaction and adhesion between the coating shell layers during heat treatment will also greatly affect the dispersion performance of the original particles.

On the other hand, the preparation of nano-scale crystalline zirconia hollow spheres by chemical methods is rarely reported in China, and the most common method for preparing such hollow spheres is the spray drying method, which requires large-scale spray drying equipment. In addition, the crystallized zirconia hollow spheres are obtained by heat-treating the organic-amorphous zirconia composite powder with a core-shell structure. However, this method also has some disadvantages such as shrinkage, cracking, and adhesion.

Contents of the invention

The invention aims at the deficiencies of the prior art, uses the alkali solution of zirconium salt as raw material, and directly covers the surface of the inorganic oxide with the nano zirconium oxide in the crystal state by the hydrothermal method. The zirconia-coated powder prepared by the method has good dispersibility, and the zirconia-coated layer has good crystallization and uniform thickness. It can resist the erosion of highly acidic (such as 1mol/L hydrochloric acid) solution for a long time and protect inorganic oxides. Hollow crystalline zirconia hollow spheres can be prepared after the coated powder prepared above is treated with concentrated hydrochloric acid with a mass fraction of 36% for a certain period of time.

In addition, by adding a certain amount of rare earth elements to the initial zirconium salt alkaline solution, heterogeneous coated powders and hollow spheres doped with rare earth elements can be prepared. The doping process is simple and easy to operate, and can be well Incorporation of rare earth elements into the zirconia lattice.

The method for preparing crystalline zirconia-coated inorganic oxide powder proposed by the present invention, its specific process steps are as follows:

(1) Preparation of crystalline zirconia uniformly coated nano-scale inorganic oxide particles by hydrothermal method:

a. Configure an alkaline solution of zirconium salt for coating, the concentration of zirconium is 0.1mmol/L～10mol/L, and the pH of the solution>9; the selected zirconium salt can be zirconium oxychloride, zirconium chloride, zirconium nitrate , zirconium sulfate, zirconium oxynitrate;

In the zirconium salt alkaline solution, preferably add the soluble salt of rare earth element, make it dissolve in this alkaline solution; The preferred soluble salt of rare earth element is yttrium nitrate, lanthanum nitrate, and preferred addition amount is the amount of the substance of zirconium 0.01% to 10%.

b. Add the inorganic oxide particles into the above zirconium salt solution, and disperse them ultrasonically for 1 to 60 minutes; the inorganic oxide can be any inorganic oxide that does not react with zirconia, preferably iron oxide, copper oxide, zinc oxide , one of inorganic oxides such as nickel oxide; the particle size of the inorganic oxide is preferably 50 nm to 5 μm, and the concentration is 0.1 g/L to 100 g/L.

c. Put the above-mentioned inorganic oxide dispersion system into the reaction kettle, the filling rate of the reaction kettle is 5% to 98%, and seal the kettle;

d. Heat the stainless steel reaction kettle at a temperature of 100-350°C and keep it warm for 10 minutes to 72 hours;

e. Cool the stainless steel reactor to room temperature, take out the product, and centrifuge at a low speed for 10 minutes to remove the excess zirconia nanocrystal grains in the upper layer, and then disperse, centrifuge, and separate the zirconia nanocrystal grains several times;

f. After the separated powder is dried, crystalline zirconia-coated inorganic oxide powder is prepared, and the thickness of the zirconia coating layer is between 5nm and 100nm;

g. To prepare a thicker crystalline zirconia coating layer, the above steps b to f can be repeated until the desired thickness is reached.

(2) The preparation method of crystalline zirconia hollow spheres:

a. Disperse the crystalline zirconia-coated inorganic oxide nanopowder prepared in step (1) in concentrated hydrochloric acid with a mass fraction of 10-50%, and let it stand for 30min-6h to dissolve the coated inorganic oxide thing;

b. Centrifuge the powder after the above-mentioned acid dissolution, and disperse and wash it several times with distilled water;

c. Dry the cleaned powder to obtain crystalline zirconia hollow balls, and the wall thickness of the hollow balls is equivalent to the thickness of the original coating layer.

The preparation method provided by the present invention is a hydrothermal method, and the coated raw material is the powder of inorganic oxides. The prepared coated powder and zirconia hollow spheres are subjected to transmission electron microscope (TEM), field emission scanning electron The morphology and structure were characterized by microscopy (FESEM). The composition and crystal phase of the coated product were identified by energy spectrum analysis (EDS), X-ray diffraction pattern (XRD) and selected area electron diffraction (SAED).

The crystalline zirconia heterogeneously coated powder prepared by the present invention has a structure of crystalline zirconia-coated inorganic oxide powder, and the inorganic oxide can be any inorganic oxide that does not react with zirconia. The preferred inorganic oxide is one of iron oxide, copper oxide, zinc oxide, nickel oxide and other inorganic oxides, the thickness of the zirconia coating layer is 5nm-100nm, and the particle size of the powder is 50-200nm; The crystalline zirconia is preferably doped with yttrium or lanthanum, and the preferred doping amount is 0.01% to 10% of the amount of zirconium.

The crystalline zirconia heterogeneously coated hollow spheres prepared by the present invention have a structure of crystalline zirconia hollow spheres, the wall thickness of the hollow spheres is 5nm-100nm, and the particle diameter of the spheres is 50-200nm; The zirconium oxide in the zirconium state is preferably doped with yttrium or lanthanum, and the preferred doping amount is 0.01% to 10% of the amount of zirconium. .

The present invention mainly uses the hydrothermal method to directly prepare crystalline zirconia-coated inorganic oxide powder, and further prepares crystalline zirconia hollow spheres, and can prepare doped crystals by doping some rare earth elements. Zirconia coated powder and hollow balls. The process is simple and easy to operate, and has low requirements for raw materials and equipment. Various surfactants can be added according to actual needs, and crystalline zirconia-coated powder and hollow spheres can be directly synthesized in the solution. In addition, water and inorganic zirconium salts are used as raw materials in the experiment, which has low cost and can reduce environmental pollution as much as possible.

Description of drawings

Fig. 1 is a transmission electron micrograph (TEM) of the crystalline zirconia-coated iron oxide powder in Example 1.

Fig. 2 is the spectrum (EDS) of the energy spectrum analysis of the coated powder shell layer of Example 1.

Fig. 3 is an X-ray diffraction pattern (XRD) of the crystalline zirconia-coated iron oxide powder in Example 1.

Fig. 4 is a transmission electron micrograph (TEM) of the crystalline zirconia-coated iron oxide powder in Example 2.

Fig. 5 is the selected area electron diffraction spot (SAED) of the coated powder of Example 2.

Fig. 6 is a transmission electron micrograph (TEM) of the crystalline zirconia hollow spherical powder of Example 2.

Fig. 7 is a transmission electron micrograph (TEM) of the crystalline zirconia hollow spherical powder of Example 3.

Fig. 8 is a field emission scanning electron micrograph (SEM) of the crystalline zirconia hollow spherical powder of Example 3.

Fig. 9 is an energy spectrum analysis spectrum (EDS) of the crystalline zirconia hollow spherical powder doped in Example 4.

Detailed ways

Example 1

First prepare an aqueous solution of zirconium oxychloride, take 1.61 g of zirconium oxychloride octahydrate (ZrOCl ₂ 8H ₂ O) and dissolve it in 30 mL of deionized water, and adjust the pH value of the zirconium solution to around 11 with 1 mol/L KOH solution , with a volume of 50 mL. Add 0.020 g of iron oxide to the obtained basic zirconium solution, and ultrasonically disperse for 10 min. The dispersed solution was charged into a 70 mL stainless steel reaction kettle with a polytetrafluoroethylene liner. After sealing the kettle, it was placed in an oven at 160°C. Take it out after 2 hours, and let it cool down to room temperature naturally in the air. Then the powder was taken out from the reaction kettle, and the milky white nano-powder in the upper layer was removed after centrifugation at a speed of 2000 rpm. Then, after the separated product is dispersed, it is centrifuged again. After several times, the obtained powder is dried in an oven at 60° C. to obtain crystalline zirconia heterogeneously coated particles. The particle size of the iron oxide core of the heterogeneously coated powder is 50-200 nm, and the thickness of the crystalline zirconia of the coated shell layer is 8-10 nm.

Example 2

First configure the aqueous solution of zirconium oxychloride, take 0.19 g of zirconium oxychloride octahydrate (ZrOCl ₂ 8H ₂ O) and dissolve it in 6 mL of deionized water, and prepare 1 mol/L potassium hydroxide (KOH) and potassium carbonate ( K ₂ CO ₃ ) solution. Adjust the pH of the zirconium solution to 12 with the above two alkali solutions, and the volume is 60mL, then add 0.03g of iron oxide and 1% polyvinylpyrrolidone (PVP) solution as a dispersant to the obtained alkaline zirconium solution, and disperse by ultrasonic for 15min . The dispersed solution was loaded into a small stainless steel reaction kettle with a polytetrafluoroethylene liner with a volume of 70 mL. After the kettle was sealed, it was placed in an oven at 160°C, taken out after 48 hours, and naturally cooled to room temperature in the air. Then the powder was taken out from the reaction kettle, and the milky white nano-powder in the upper layer was removed after centrifugation at a speed of 2000 rpm. Then, after the separated product is dispersed, it is centrifuged again. After several times, the obtained powder is dried in an oven at 60° C. to obtain crystalline zirconia heterogeneously coated particles. The particle diameter of the iron oxide core of the coated particle is 50-150 nm, and the thickness of the crystalline zirconia of the coated shell layer is 10-12 nm.

Disperse the core-shell structure powder obtained above in hydrochloric acid with a mass fraction of 36% and dissolve for 3 hours, then centrifuge, wash, and re-separate several times to obtain hollow spheres of crystalline zirconia. The wall thickness of the hollow sphere is about 10 nm.

Example 3

First configure the aqueous solution of zirconium oxychloride, take 0.19 g of zirconium oxychloride octahydrate (ZrOCl ₂ 8H ₂ O) and dissolve it in 3 mL of deionized water, and prepare 1 mol/L potassium hydroxide (KOH) and potassium carbonate ( K ₂ CO ₃ ) solution. The pH of the zirconium solution was adjusted to 11 with the above two alkali solutions, and the volume was 60 mL, and then 0.03 g of iron oxide was added to the obtained alkaline zirconium solution, and ultrasonically dispersed for 10 min. The dispersed solution was charged into a 70 mL stainless steel reaction kettle with a polytetrafluoroethylene liner. After sealing the kettle, it was placed in an oven at 160°C. Take it out after 12 hours, and let it cool down to room temperature naturally in the air. Then the powder is transferred out from the reaction kettle, and the milky white nano-powder in the upper layer is removed after centrifugation at a speed of 2000 rpm. Then, after the separated product is dispersed, it is centrifuged again. After several times, the obtained powder is dried in a 60° oven to obtain crystalline zirconia heterogeneously coated particles. Disperse the coated powder once again in the 60mL zirconium alkaline solution prepared above, repeat the above hydrothermal step once, then centrifuge several times and dry to obtain a thicker zirconia coated powder. Coated iron oxide powder. The particle diameter of the iron oxide core of the coated particle is 100-200nm, and the thickness of the crystalline zirconia of the coated shell layer is 20-30nm.

Finally, the obtained powder with core-shell structure was dispersed in hydrochloric acid with a mass fraction of 36% and dissolved for 6 hours, followed by centrifugation, washing, and separation several times to obtain hollow spheres of crystalline zirconia. The wall thickness of the hollow sphere is about 20-30nm.

Example 4

First configure the aqueous solution of zirconium oxychloride, take 0.19 g of zirconium oxychloride octahydrate (ZrOCl ₂ 8H ₂ O) and dissolve it in 3 mL of deionized water, and prepare 1 mol/L potassium hydroxide (KOH) and potassium carbonate ( K ₂ CO ₃ ) solution. The pH of the zirconium solution was adjusted to 12 with the above two alkali solutions, and the volume was 60 mL, and then 0.016 g of yttrium nitrate hexahydrate (Y(NO ₃ ) ₃ ·6H ₂ O) was added to the obtained basic zirconium solution until it was completely dissolved. Finally, 0.03 g of iron oxide was added to the solution, and ultrasonically dispersed for 10 min. The dispersed solution was charged into a 70 mL stainless steel reaction kettle with a polytetrafluoroethylene liner. After sealing the kettle, it was placed in an oven at 160°C. Take it out after 12 hours, and let it cool down to room temperature naturally in the air. Then the powder is transferred out from the reaction kettle, and the milky white nano-powder in the upper layer is removed after centrifugation at a speed of 2000 rpm. Then, the isolated product is dispersed, and then centrifuged. After several times, the obtained powder is dried in a 60° oven to obtain yttrium-doped crystalline zirconia heterogeneously coated particles. The particle diameter of the iron oxide core of the coated particle is 50-150nm, and the thickness of the yttrium-doped crystalline zirconia of the coated shell layer is 10-12nm.

Finally, the obtained core-shell structure powder is dispersed in hydrochloric acid with a mass fraction of 36% and dissolved for 6 hours, followed by centrifugation, cleaning, and separation several times to obtain the hollow core of yttrium-doped crystalline zirconia. ball. The wall thickness of the hollow sphere is about 10-15 nm.

Claims (15)

1. Crystalline zirconia heterogeneously coated powder, characterized in that its structure is crystalline zirconia-coated inorganic oxide powder, and the inorganic oxide is any inorganic oxide that does not react with zirconia The thickness of the zirconia coating layer is 5nm-100nm, and the particle size of the powder is 50-200nm. 2. The crystalline zirconia heterogeneously coated powder according to claim 2, wherein said inorganic oxide is one of iron oxide, copper oxide, zinc oxide and nickel oxide. 3. The crystalline zirconia heterogeneously coated powder according to claim 1 or 2, characterized in that the crystalline zirconia is doped with yttrium or lanthanum. 4. The crystalline zirconia heterogeneously coated powder according to claim 3, characterized in that said doping amount is 0.01%-10% of the amount of zirconium. 5. The preparation method of crystalline zirconia heterogeneously coated powder, characterized in that it comprises the following steps: (1) Configure zirconium salt alkaline solution, the concentration of zirconium is 0.1mmol/L～10mol/L, and the pH of the solution>9; (2) adding the inorganic oxide particles into the above-mentioned zirconium salt solution, and ultrasonically dispersing for 1 to 60 minutes; (3) above-mentioned product is packed into reaction kettle, and the filling rate of reaction kettle is 5%～98%, seals still; (4) heat preservation at 100-350°C for 10 minutes-72 hours; (5) separation product; (6) Repeat the above steps (1) to (5) several times according to the thickness of the coating. 6. The method for preparing crystalline zirconia heterogeneously coated powder according to claim 5, wherein said inorganic oxide is one of iron oxide, copper oxide, zinc oxide and nickel oxide. 7. The method for preparing crystalline zirconia heterogeneously coated powder according to claim 5 or 6, characterized in that the particle size of the inorganic oxide is 50nm-5μm, and the concentration is 0.1g/L- 100g/L. 8. The method for preparing crystalline zirconia heterogeneously coated powder according to claim 5, wherein the zirconium salt is zirconium oxychloride, zirconium chloride, zirconium nitrate, zirconium sulfate or oxygen nitrate zirconium. 9. Crystalline zirconia heterogeneously coated hollow spheres, characterized in that the structure is crystalline zirconia hollow spheres, the wall thickness of the hollow spheres is 5nm-100nm, and the particle size of the spheres is 50-200nm; 10. The crystalline zirconia heterogeneously coated hollow sphere according to claim 9, characterized in that the crystalline zirconia is doped with yttrium or lanthanum. 11. The crystalline zirconia heterogeneously coated hollow sphere according to claim 10, characterized in that the doping amount is 0.01%-10% of the amount of zirconium. 12. A method for preparing hollow spheres coated with crystalline zirconia heterogeneously, comprising the following steps: (1) Configure zirconium salt alkaline solution, the concentration of zirconium is 0.1mmol/L～10mol/L, and the pH of the solution>9; (2) adding the inorganic oxide particles into the above-mentioned zirconium salt solution, and ultrasonically dispersing for 1 to 60 minutes; (3) above-mentioned product is packed into reaction kettle, and the filling rate of reaction kettle is 5%～98%, seals still; (4) heat preservation at 100-350°C for 10 minutes-72 hours; (5) separation product; (6) Repeat the above steps (1) to (5) several times according to the thickness of the coating; (7) Disperse the product prepared in step (6) in concentrated hydrochloric acid of 10 to 50 wt%, and let it stand for 30 minutes to 6 hours; (8) Separate the product and wash. 13. The method for preparing hollow spheres coated with crystalline zirconia heterogeneously according to claim 12, wherein said inorganic oxide is one of iron oxide, copper oxide, zinc oxide and nickel oxide. 14. The method for preparing crystalline zirconia heterogeneously coated hollow spheres according to claim 12 or 13, characterized in that the particle size of the inorganic oxide is 50nm-5μm, and the concentration is 0.1g/L- 100g/L. 15. The method for preparing crystalline zirconia heterogeneously coated hollow spheres according to claim 12, wherein the zirconium salt is zirconium oxychloride, zirconium chloride, zirconium nitrate, zirconium sulfate or oxygen nitrate zirconium.

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