CN105502421B - A kind of preparation method of zinc silicate hollow sub-microsphere - Google Patents

Abstract

The invention discloses a preparation method of zinc silicate hollow microspheres. The method firstly adds thiourea solution into zinc acetate solution, mixes evenly, and reacts hydrothermally at a temperature of 100-220° C. for 6-30 hours to prepare monodisperse zinc sulfide microspheres; dry the monodisperse zinc sulfide microspheres, Add ethanol, ammonia water and ethyl orthosilicate in sequence under stirring. After stirring, monodisperse zinc sulfide@silica core-shell structure spheres are prepared. After drying, they are calcined at 800-1000°C for 18‑48h to obtain zinc silicate hollow Microspheres. The invention prepares zinc sulfide microspheres through a simple hydrothermal method, and then coats the zinc sulfide microspheres with silicon dioxide to obtain zinc sulfide@silicon dioxide core-shell structure balls, and finally calcines them to obtain zinc silicate hollow microspheres; the preparation method is novel , The reaction process does not require surfactants, and the resulting particles have high purity, controllable size, uniformity, and good dispersibility.

Description

A kind of preparation method of zinc silicate hollow microsphere

technical field

The invention relates to zinc silicate, in particular to a method for preparing zinc silicate hollow microspheres; it belongs to the technical field of preparation of inorganic nanometer powder materials.

Background technique

Inorganic phosphor is an important and inexpensive luminescent material, so its luminescent properties have been widely studied in the fields of displays and light-emitting devices. ZnO-based ternary compounds are a class of multifunctional materials, the general chemical formula is ZnM ₂ O ₄ or Zn ₂ MO ₄ , M is Al, Si, Ga, Fe, In, Sn, Sb, Ti, Mn, V, Cr, etc. . Most of these compounds are broadband semiconductors and typical phosphorescent materials, and exhibit specific functions that other common ternary compounds do not have.

The molecular formula of zinc silicate is Zn ₂ SiO ₄ , and its band gap energy is 5.5eV. Silicate has rich resources, low cost, strong environmental adaptability, relatively stable chemical properties, strong moisture resistance and other good physical and chemical properties. It has long been the focus of people's research. At present, silicates are widely used in various fields, such as fluorescent materials, mesoporous molecular sieves, catalyst carriers, gas storage, gas separation, drug slow release, cement, concrete and other building materials, and glass manufacturing.

The properties and uses of solid materials are directly related to the spatial arrangement of constituent material atoms and the morphology of materials. Using simple, green and economical methods to synthesize functional silicate nanomaterials with controllable dimensions and crystallinity is very important for the development of other materials. The new application value is of great significance. Based on the structural characteristics of silicate, many functional silicate materials have been synthesized, such as polymers with high heat resistance, high strength, flame retardancy, high wear resistance, and low expansion coefficient. Layered silicate organic-inorganic composite nanomaterials, silicate mesoporous materials, etc. Among them, silicate (micro) nano hollow spheres can improve their ability to remove noble metals (such as divalent lead, divalent chromium, and ferric ions) due to their adjustable pore size, large specific surface area, and low toxicity; The specific surface area of the hollow structure is large, which can increase the contact area with organic pollutants, thereby improving the catalytic performance; the zinc silicate microspheres with the hollow structure can also be used as nanoreactors; It can fully contact with the gas molecules to be measured, thereby improving its response sensitivity, etc.; the hollow structure of zinc silicate is also widely used in lithium-ion batteries, drug delivery, fluorescent materials and other fields.

At present, the main preparation methods of zinc silicate are traditional solid-phase synthesis method, combustion synthesis method, sol-gel method, microwave method, spray pyrolysis method, chemical precipitation method, hydrothermal synthesis method, etc. Various properties of nanomaterials are closely related to the size, particle size distribution, morphology and composition of nanocrystals. It can be seen that it is of great significance in the field of material synthesis chemistry and practical production and application to control and prepare zinc silicate nanomaterials with specific structure, morphology and size with simple, green and economical methods.

Contents of the invention

The purpose of the present invention is to overcome the defects of the existing preparation technology, and provide a method for preparing zinc silicate hollow microspheres with simple operation, low energy consumption, no need for surfactants and simple product post-treatment.

The present invention utilizes the advantages of the hydrothermal method in the preparation of new materials, and on the basis of the ZnS microspheres synthesized by the hydrothermal method, combined with the ion exchange method and the Kirkendall effect, zinc silicate is synthesized by a simple calcination method Hollow microspheres, the resulting hollow spheres are uniform in size, and their shape and size can be controlled by reaction conditions. So far, the synthesis of zinc silicate hollow microspheres by ion exchange has not been reported.

The purpose of the present invention is achieved through the following technical solutions:

A method for preparing zinc silicate hollow microspheres, characterized in that: adding thiourea solution to zinc acetate solution with a molar concentration ratio of 3:1 to 1:2, stirring until uniformly mixed, at a temperature of 100 to 220 Under the condition of ℃ hydrothermal reaction for 6 ~ 30h, monodisperse zinc sulfide microspheres were prepared; after drying, weigh 0.02 ~ 0.1g of zinc sulfide powder, add 10 ~ 40ml of ethanol, 1 ~ 5ml of 25% ammonia water, 1 ~ 5ml tetraethyl orthosilicate, after stirring for 4-10 hours, monodisperse zinc sulfide@silica core-shell structure balls were prepared; after drying, weigh 0.01-0.1g zinc sulfide@silica powder and put it in a ceramic crucible, Calcined in a muffle furnace at 800-1000°C for 18-48 hours to obtain zinc silicate hollow microspheres;

In order to further realize the object of the present invention, the molar concentration ratio of the thiourea solution and the zinc acetate solution is 2:1˜1:1.

The hydrothermal reaction is carried out in a high-pressure reactor with a polytetrafluoroethylene liner.

The temperature of the hydrothermal reaction is preferably 180-220° C., and the time of the hydrothermal reaction is preferably 8-20 hours.

The coated silicon dioxide is added with ethanol, 25% ammonia water and ethyl orthosilicate under stirring, the volumes of which are preferably 15-40ml, 2-4ml and 2-4ml respectively.

The stirring time of the coated silica is preferably 5-10 hours.

The calcination temperature is preferably 850-1000°C, and the calcination time is preferably 18-48h.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The present invention adopts a hydrothermal method to prepare zinc sulfide microspheres, which has simple operation, low energy consumption, no surfactant, and simple product post-treatment.

(2) On the basis of ZnS microspheres synthesized by hydrothermal method, combined with ion exchange method and Kirkendall effect, the present invention synthesizes zinc silicate hollow microspheres by a simple calcination method, which is a groundbreaking invention. It is difficult to obtain zinc silicate microspheres with hollow structures by general hydrothermal (solvent) methods. The present invention first synthesizes zinc sulfide structures of various shapes, and then obtains hollow structures of corresponding shapes by the method of the present invention. Zinc silicate, which provides a new way for the preparation of zinc silicate.

(3) The orthorhombic zinc silicate microspheres obtained in the present invention have a hollow structure, and the obtained particles have high purity, controllable and uniform size, and good dispersibility.

Description of drawings

Fig. 1 (a) is the X-ray diffraction figure of the zinc sulfide microsphere prepared by embodiment 1;

Figure 1(b) is a scanning electron micrograph of the zinc sulfide microspheres prepared in Example 1.

Fig. 2 (a) is the X-ray diffraction diagram of the zinc sulfide@silica core-shell structure sphere prepared in Example 1;

Figure 2(b) is a scanning electron micrograph of the zinc sulfide@silica core-shell structure sphere prepared in Example 1.

FIG. 3 is an X-ray diffraction pattern of zinc silicate hollow microspheres prepared in Example 1.

4 is a scanning electron micrograph of the zinc silicate hollow microspheres prepared in Example 1.

5 is a transmission electron micrograph of the zinc silicate hollow microspheres prepared in Example 1.

6 is a scanning electron micrograph of the zinc silicate hollow microspheres prepared in Example 3.

Detailed ways

In order to better understand the present invention, the present invention will be further described below in conjunction with the accompanying drawings and examples, but the protection scope of the present invention is not limited to the scope described in the examples.

Example 1

Slowly add 0.8mol/L thiourea solution into 0.4mol/L zinc acetate solution, the volume ratio of thiourea solution to zinc acetate solution is 1:1, stir until evenly mixed, and then hydrothermally react at a temperature of 180°C for 10 hours , prepared monodisperse zinc sulfide microspheres; the X-ray diffraction pattern and scanning electron microscope photographs of the resulting zinc sulfide microspheres are shown in Figure 1(a) and Figure 1(b) respectively. It can be seen from Figure 1(a) that the peak position of each diffraction peak is consistent with the diffraction peak position on the standard card (JCPDS No.77-2100) of cubic phase ZnS, and no impurity peak appears, indicating that the product is pure cubic phase ZnS . From Figure 1(b), it can be seen that ZnS microspheres are solid spheres with a diameter of 3-5 μm, which are piled up by numerous nanoparticles, and the surface of the spheres is smooth. After drying, weigh 0.05g of zinc sulfide powder, add 20ml of ethanol, 2ml of 25% ammonia water, and 2ml of ethyl orthosilicate in turn under stirring, and after stirring for 6 hours, monodisperse zinc sulfide@silica core-shell structure balls are prepared (ZnS@SiO ₂ core-shell structure sphere). Figure 2(a) is the XRD spectrum of the ZnS@SiO ₂ core-shell structure sphere. It can be seen from the figure that the ZnS@SiO ₂ core-shell structure sphere after coating is still the peak of the cubic phase ZnS, but the intensity ratio of the peak is The one before coating is weaker and rougher, which may be caused by the amorphous SiO ₂ on the surface of ZnS spheres. A broad peak around 22° is the glassy phase peak of SiO ₂ . Figure 2(b) is a scanning electron microscope photo of ZnS@SiO ₂ core-shell structure spheres. It can be seen that the surface of ZnS microspheres changes from smooth to rough, and there are many amorphous SiO ₂ coated on the microspheres. The diameter of the ZnS microspheres after coating is larger than that before coating; it can also be seen that there are a lot of amorphous SiO ₂ randomly scattered around; the thickness of the shell layer of SiO ₂ can be changed by changing the amount of tetraethyl silicate or Repeat the SiO ₂ coating process several times to adjust.

After drying, weigh 0.02g of zinc sulfide@silica powder, place it in a ceramic crucible, and calcinate it in a muffle furnace at 900°C for 24 hours to obtain zinc silicate hollow microspheres. The X-ray diffraction pattern of the gained zinc silicate hollow microspheres is as shown in Figure 3, and it can be seen that the product at this time is the peak of Zn ₂ SiO ₄ (JCPDS No.37-1485), and substantially no other peaks exist, which means It may be that zinc sulfide and SiO ₂ are completely transformed into Zn ₂ SiO ₄ hollow microspheres through the Kirkendall effect as the reaction time prolongs. The morphology of the zinc silicate hollow microspheres is shown in Figure 4. It can be seen from the SEM photos that the synthesized Zn ₂ SiO ₄ microspheres become hollow and some are partially broken. The diameter of the ball is about 3 μm, and the spherical shell is relatively thin, with a thickness of 100 to 300 nm. The resulting product was further analyzed by TEM, and the results are shown in FIG. 5 . It can be seen from the transmission electron microscope of the sample that the obtained product is a hollow Zn ₂ SiO ₄ micron sphere, and the surface of the sphere is formed by accumulation of nanoparticles, and the diameter of the particle is about 500nm.

Chinese invention patent 2006100404227 discloses a composite hollow sphere composed of radially closely packed zinc silicate nanowires and a preparation method thereof, which includes the following steps: (1) firstly mix carbonate and carbon powder in a molar ratio of 2:0.8 to 1.2 Mix, and then cover the mixture with zinc powder with a thickness of 1 to 3 mm. (2) Firstly, the mixture covered with zinc powder and silicon wafer are kept at 400 to 500 ° C for 3 to 7 minutes in an argon atmosphere, and then the It is kept at 900-1100 DEG C in an argon atmosphere for 1-3 hours to prepare a composite hollow sphere composed of radially closely packed zinc silicate nanowires. The carbonate is zinc carbonate, magnesium carbonate or manganese carbonate, and the distance between the zinc powder-coated mixture and the silicon sheet is 6-10 cm. However, this technology requires high-temperature calcination in an argon atmosphere, the preparation conditions are harsh, and the production cost is high. At the same time, high-purity zinc silicate microspheres that are completely empty cannot be obtained. It is well known that (micro) nano hollow spheres have high catalytic and adsorption properties due to their high specific surface area and low density. It is difficult to obtain zinc silicate microspheres with a hollow structure by general hydrothermal (solvent) method. The present invention obtains zinc silicate hollow microspheres by using a simple calcination method, which is the first time that zinc silicate hollow microspheres are synthesized by ion exchange. Balls provide a more practical method for preparing zinc silicate hollow structures.

Example 2

Slowly add 0.8mol/L thiourea solution into 0.4mol/L zinc acetate solution, the volume ratio of thiourea solution to zinc acetate solution is 1.5:1, stir until evenly mixed, and then hydrothermally react at 180°C for 12 hours , to prepare monodisperse zinc sulfide microspheres; weigh 0.1g of zinc sulfide powder after drying, add 40ml of ethanol, 4ml of 25% ammonia water, and 4ml of ethyl orthosilicate successively under stirring, and after stirring for 6 hours, a monodisperse Zinc sulfide@silica core-shell structure spheres. After drying, weigh 0.02g of zinc sulfide@silica powder, place it in a ceramic crucible, and calcinate it in a muffle furnace at 900°C for 20 hours to obtain zinc silicate hollow microspheres. The appearance of the X-ray diffraction pattern and the scanning electron micrograph of the zinc sulfide microspheres obtained in this embodiment are similar to those shown in FIG. 1 . The X-ray diffraction pattern of the obtained zinc silicate hollow microspheres is completely consistent with the standard peak of zinc silicate (JCPDS No. 37-1485), and the morphology is similar to that shown in Figure 4.

Example 3

Slowly add 0.4mol/L thiourea solution into 0.2mol/L zinc acetate solution, the volume ratio of thiourea solution to zinc acetate solution is 1:1, stir until the mixture is uniform, and then hydrothermally react for 20 hours at a temperature of 180°C , to prepare monodisperse zinc sulfide microspheres; weigh 0.08g of zinc sulfide powder after drying, add 32ml of ethanol, 3.2ml of 25% ammonia water, and 3.2ml of ethyl orthosilicate successively under stirring, and after stirring for 10h, prepare Monodisperse zinc sulfide@silica core-shell structured spheres. After drying, weigh 0.05g of zinc sulfide@silica powder, place it in a ceramic crucible, and calcinate it in a muffle furnace at 900°C for 48 hours to obtain zinc silicate hollow microspheres. The X-ray diffraction pattern of the obtained zinc silicate hollow microspheres is completely consistent with the standard peak of zinc silicate (JCPDS No. 37-1485), and the morphology is shown in FIG. 6 . It can be seen from the SEM photos that the synthesized Zn ₂ SiO ₄ micron spheres become empty and some are partially broken. The diameter of the ball is about 2 to 3 μm, and the spherical shell is relatively thin, with a thickness of 300 to 500 nm.

Example 4

Slowly add 0.8mol/L thiourea solution into 0.4mol/L zinc acetate solution, the volume ratio of thiourea solution to zinc acetate solution is 2:1.5, stir until the mixture is uniform, and react hydrothermally at 200°C for 12 hours , to prepare monodisperse zinc sulfide microspheres; weigh 0.05g of zinc sulfide powder after drying, add 25ml of ethanol, 4ml of 25% ammonia water, and 4ml of ethyl orthosilicate successively under stirring, and after stirring for 8 hours, monodisperse Zinc sulfide@silica core-shell structure spheres. After drying, weigh 0.04g of zinc sulfide@silica powder, place it in a ceramic crucible, and calcinate it in a muffle furnace at 1000°C for 24 hours to obtain zinc silicate hollow microspheres. The obtained zinc silicate hollow microsphere X-ray diffraction pattern is shown in Figure 3, and its appearance is similar to Figure 5.

Example 5

Slowly add 0.4mol/L thiourea solution into 0.2mol/L zinc acetate solution, the volume ratio of thiourea solution to zinc acetate solution is 1.2:1, stir until evenly mixed, then hydrothermally react at 220°C for 10 hours , to prepare monodisperse zinc sulfide microspheres; weigh 0.05g of zinc sulfide powder after drying, add 20ml of ethanol, 2ml of 25% ammonia water, and 4ml of ethyl orthosilicate successively under stirring, and after stirring for 8 hours, a monodisperse Zinc sulfide@silica core-shell structure spheres. After drying, weigh 0.10g of zinc sulfide@silica powder, place it in a ceramic crucible, and calcinate it in a muffle furnace at 1000°C for 20 hours to obtain zinc silicate hollow microspheres. The X-ray diffraction pattern of the obtained zinc silicate hollow microspheres completely coincides with the standard peak of zinc silicate (JCPDS No.37-1485). The appearance is similar to that shown in Figure 4.

On the basis of the ZnS microspheres synthesized by the hydrothermal method, combined with the ion exchange method and the Kirkendall effect, the present invention synthesizes the zinc silicate hollow microspheres by a simple calcination method, which is the existing preparation method of the zinc silicate hollow microspheres breakthrough. It is difficult to obtain zinc silicate microspheres with hollow structures by general hydrothermal (solvent) methods. The present invention first synthesizes zinc sulfide structures of various shapes, and then obtains hollow structures of corresponding shapes by the method of the present invention. Zinc silicate. This provides a new way for the preparation of zinc silicate.

The invention adopts a hydrothermal method to prepare zinc sulfide microspheres, only uses water or alcohol as a solvent, has simple operation, low energy consumption, less pollution, no surfactant is needed in the reaction process, and the post-treatment of the product is simple without special treatment of the product.

Claims (7)

1. a preparation method of zinc silicate hollow microspheres, characterized in that it may further comprise the steps: 1) Add the thiourea solution into the zinc acetate solution, control the molar concentration ratio of thiourea and zinc acetate to 3:1~1:2, stir until the mixture is uniform, and react hydrothermally at a temperature of 180~220°C for 10~20h , preparing monodisperse zinc sulfide microspheres; 2) Dry the monodisperse zinc sulfide microspheres, add ethanol, ammonia water and ethyl orthosilicate in sequence under stirring, and after stirring for 4-10 hours, prepare monodisperse zinc sulfide@silica core-shell structure spheres; 3) Monodisperse zinc sulfide@silica core-shell structure spheres are dried and calcined at 800-1000° C. for 18-48 hours to obtain zinc silicate hollow microspheres. 2. The preparation method of zinc silicate hollow microspheres according to claim 1, characterized in that: the hydrothermal reaction is carried out in a high-pressure reactor with a polytetrafluoroethylene lining. 3. the preparation method of zinc silicate hollow microsphere according to claim 1 is characterized in that: according to every 0.1g monodisperse zinc sulfide microsphere meter, add ethanol, ammoniacal liquor and orthosilicate ethyl ester respectively 10～40ml, 1~5ml and 1~5ml. 4. The preparation method of zinc silicate hollow microspheres according to claim 1, characterized in that: the mass concentration of the ammonia water is 25%. 5. The preparation method of zinc silicate hollow microspheres according to claim 1, characterized in that: the stirring time in step (2) is 5-8 hours, and the stirring speed is 300-600 r/min. 6. The preparation method of zinc silicate hollow microspheres according to claim 1, characterized in that: the calcination time is 25-35 hours. 7. The preparation method of zinc silicate hollow microspheres according to claim 1, characterized in that: the calcination is carried out in a muffle furnace.