CN110683860B - Ceramic hollow ball with double-shell structure and preparation method thereof - Google Patents

Ceramic hollow ball with double-shell structure and preparation method thereof Download PDF

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CN110683860B
CN110683860B CN201911128772.2A CN201911128772A CN110683860B CN 110683860 B CN110683860 B CN 110683860B CN 201911128772 A CN201911128772 A CN 201911128772A CN 110683860 B CN110683860 B CN 110683860B
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gelatin
ball
double
ceramic hollow
shell structure
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CN110683860A (en
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郭新爽
王献忠
段娜娜
颜嘉威
万力
闵俊豪
祝嘉诚
黄葳
谢新泰
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First Affiliated Hospital of Henan University of Science and Technology
Pingxiang University
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Pingxiang University
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Abstract

The invention relates to a ceramic hollow sphere with a double-shell structure and a preparation method thereof, belongs to the technical field of ceramics, and solves the problems that the effective specific surface area of the existing ceramic hollow sphere is smaller or the catalytic effect is poorer because the existing ceramic hollow sphere only has a single-layer spherical shell. The ceramic hollow ball with the double-shell structure comprises an outer shell layer and an inner shell layer, wherein the outer shell layer is connected with the inner shell layer; a plurality of micropores are distributed on the outer shell layer and the inner shell layer. The preparation method comprises the following steps: preparing gelatin microspheres; pelletizing; drying and sintering the composite ball to obtain the ceramic hollow ball with the double-shell structure. The preparation method of the ceramic hollow sphere with the double-shell structure can be used for preparing the ceramic hollow sphere with the double-shell structure, and the ceramic hollow sphere with the double-shell structure can be used in the fields of filtration and catalysis.

Description

Ceramic hollow ball with double-shell structure and preparation method thereof
Technical Field
The invention relates to the technical field of ceramics, in particular to a ceramic hollow sphere with a double-shell structure and a preparation method thereof.
Background
Ceramic hollow spheres, such as alumina, silica and zirconia ceramic hollow spheres, are widely applied to the fields of heat insulation materials, petrochemical industrial gasification furnaces, catalyst carriers, flue gas filtration, water body purification and the like due to the characteristics of light weight, high strength, high temperature resistance, good heat insulation and the like.
The ceramic hollow spheres are generally prepared by a spray granulation method, a melt blowing method, a template ball-and-ball method and the like. The spray granulation method is that ceramic slurry is atomized, atomized liquid drops are dried to form spherical particles, and the spherical particles are subjected to heat treatment to obtain ceramic hollow spheres; the melt blowing method is formed by blowing high-temperature molten raw materials through high-speed airflow; the template ball-and-ball method is to use removable pore-forming agent as template (mother ball), and to prepare composite ball by ball-and-ball or other processes and to sinter it to obtain the hollow ceramic ball. At present, the method for industrially producing the ceramic hollow sphere mainly utilizes a melt blowing method and a template ball-and-ball method. The former has higher energy consumption, the ceramic hollow ball has low proportion, and the latter has wide universality and is convenient to operate and has great attention.
Although the ceramic hollow spheres have been prepared for many years, the prepared ceramic hollow spheres usually have compact surfaces or only a single-layer spherical shell, so that the effective specific surface area in practical application is small, and the filtering or catalytic effect is poor.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a hollow ceramic sphere with a double-shell structure and a preparation method thereof, which can solve at least one of the following technical problems: (1) the surface of the existing ceramic hollow ball is compact; (2) the existing ceramic hollow ball only has a single-layer ball shell; (3) the effective specific surface area is small, and the filtering or catalyzing effect is poor.
The purpose of the invention is mainly realized by the following technical scheme:
on one hand, the invention discloses a ceramic hollow ball with a double-shell structure, which comprises an outer shell layer and an inner shell layer, wherein the outer shell layer is connected with the inner shell layer; a plurality of micropores are distributed on the outer shell layer and the inner shell layer.
In one possible design, the specific surface area of the ceramic hollow sphere with the double-shell structure is 0.62-5.9m2/g。
On the other hand, the invention discloses a preparation method of a ceramic hollow sphere with a double-shell structure, which comprises the following steps:
step 1, preparing gelatin microspheres;
step 2, putting the gelatin microspheres prepared in the step 1 into a ball forming machine, uniformly mixing ceramic raw material powder, a binder and a sintering aid to obtain mixed powder, uniformly scattering the mixed powder on the surfaces of the gelatin microspheres, and starting the ball forming machine to form balls to obtain composite balls with the surfaces of the gelatin microspheres uniformly coated with the mixed powder;
and 3, drying and sintering the composite ball to obtain the ceramic hollow ball with the double-shell structure.
In one possible design, step 1 includes:
s11, weighing gelatin, and dissolving the gelatin in water at 40-60 ℃ to obtain a gelatin solution;
step S12, dripping the prepared gelatin solution into soybean oil, and preparing gelatin balls through magnetic stirring;
step S13, putting the formed gelatin ball into a cross-linking agent for treatment;
and S14, filtering the gelatin spheres processed in the step S13 by using a filter screen, cleaning by using a detergent, and air-drying surface moisture at 20-25 ℃ after cleaning to prepare the gelatin microspheres.
In one possible design, in step S11, the concentration of the gelatin solution is 150-260 g/L.
In one possible design, in step S12, the stirring speed of the magnetic stirring is 130-200 r/min.
In one possible design, in step 2, the ceramic raw material powder, the sintering aid and the binder are equally divided into a plurality of equal parts, and each equal part is sequentially added into the container according to the sequence of the ceramic raw material powder, the sintering aid and the binder and is uniformly mixed.
In a possible design, in the step 2, the rotating speed of the ball forming machine is 10-50 r/min.
In one possible design, in the step 3, the composite balls are dried for 12-36 hours at the temperature of 20-25 ℃.
In one possible design, in step 3, the sintering temperature is 1100-1550 ℃.
Compared with the prior art, the invention can realize at least one of the following beneficial effects:
(1) the ceramic hollow ball with the double-shell structure has the double-shell structure comprising the outer shell layer and the inner shell layer, and the outer shell layer and the inner shell layer are both provided with the microporous structures, so that compared with the traditional ceramic hollow ball with the single-shell structure, the ceramic hollow ball with the double-shell structure has higher specific surface area, and has wide application prospects in the fields of filtration, catalyst carriers and the like.
(2) According to the preparation method of the ceramic hollow sphere with the double-shell structure, the gelatin microsphere is prepared firstly, the mixed powder is uniformly scattered on the surface of the gelatin microsphere and then the gelatin microsphere is agglomerated, and finally the composite sphere is dried and sintered, so that the ceramic hollow sphere with the double-shell structure can be obtained, and the preparation method is simple in technological process and strong in operability.
(3) According to the method, the concentration, the stirring speed, the water-oil ratio and the concentration of the cross-linking agent of the gelatin solution are accurately controlled in the process of preparing the gelatin microspheres, and the gelatin microspheres with good roundness and dispersity and uniform size can be obtained.
(4) In the process of preparing the composite balls, the composite balls with good roundness and dispersity and uniform size can be obtained by controlling the preparation method of the mixed powder, the proportion of the mixed powder, the rotating speed of the ball-making machine and the ball-making time.
(5) This application is in the drying and sintering process of composite ball, and the structure of avoiding composite ball through control temperature and time collapses, finally obtains the ceramic hollow ball of the double shell structure that the size is even, the circularity is good, the structure is complete.
In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the embodiments and instrumentalities pointed out in the specification and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention.
FIG. 1 is an optical diagram of gelatin microspheres of example 1 of the present invention;
FIG. 2 is an optical diagram of a plurality of hollow ceramic balls having a double shell structure according to example 1 of the present invention;
FIG. 3 is an SEM image of a hollow ceramic sphere having a double shell structure according to example 1 of the present invention;
FIG. 4 is an SEM image of a hollow ceramic sphere of double shell structure with a broken outer shell layer according to example 1 of the present invention;
FIG. 5 is an SEM photograph of a hollow ceramic sphere having a double shell structure with inner and outer shell layers broken according to example 1 of the present invention;
FIG. 6 is a surface SEM image of an outer shell layer of a ceramic hollow sphere having a double-shell structure according to example 1 of the present invention;
FIG. 7 is a schematic structural view of a ceramic hollow sphere having a double shell structure according to the present invention.
Reference numerals:
1-an outer shell layer; 2-inner shell layer.
Detailed Description
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.
The application provides a ceramic hollow sphere with a double-shell structure, as shown in fig. 7, the ceramic hollow sphere with the double-shell structure comprises an outer shell layer 1 and an inner shell layer 2, wherein the outer shell layer 1 is partially connected with the inner shell layer 2; a plurality of micropores are uniformly distributed on the outer shell layer 1 and the inner shell layer 2.
Specifically, the inner wall of the outer shell layer 1 is connected with the outer wall of the inner shell layer 2, one part of the outer wall of the inner shell layer 2 is connected with one part of the inner wall of the outer shell layer 1 through a point or a surface, and the inner shell layer 2 is attached to or supported in the outer shell layer 1 through the connecting point or the connecting surface.
Specifically, the diameter of the micropores is 0.1-15 μm.
Specifically, the outer diameter of the outer shell 1 of the ceramic hollow sphere with a double-shell structure0.68-1.2 mm, the thickness of the outer shell layer 1 is 71-120 mu m, the outer diameter of the inner shell layer 2 is 0.45-0.72 mm, the thickness of the inner shell layer 2 is 40-100 mu m, and the density of the ceramic hollow sphere is 0.3-0.8 g/cm3The roundness is 0.085-0.12, the porosity is 63% -83%, and the specific surface area is 0.62-5.9m2/g。
Compared with the prior art, the ceramic hollow sphere of double-shell structure that this application provided is owing to have the double-shell structure of outer shell and inner shell to all have microporous structure on outer shell and the inner shell, therefore this kind of double-shell structure's ceramic hollow sphere specific surface is high, and ceramic hollow sphere has extensive application prospect in fields such as filtration and catalyst carrier.
The application also provides a preparation method of the ceramic hollow sphere with the double-shell structure, which comprises the following steps:
step 1, preparing gelatin microspheres;
and 2, putting the gelatin microspheres prepared in the step 1 into a ball forming machine, uniformly mixing the ceramic raw material powder, the sintering aid and the binder to obtain mixed powder, uniformly scattering the mixed powder on the surfaces of the gelatin microspheres, and starting the ball forming machine to form balls to obtain the composite balls with good roundness and dispersity, wherein the surfaces of the gelatin microspheres are uniformly wrapped with the mixed powder.
And 3, drying and sintering the composite ball to obtain the ceramic hollow ball with the double-shell structure.
Exemplarily, the step 1 includes:
s11, weighing gelatin, and dissolving the gelatin in water at 40-60 ℃ to obtain a gelatin solution;
step S12, dripping the prepared gelatin solution into soybean oil, and preparing gelatin balls through magnetic stirring;
s13, placing the formed gelatin balls into a cross-linking agent for treatment, wherein the volume ratio of the gelatin balls to the cross-linking agent is 1/2-1/5;
and S14, filtering the gelatin ball processed in the step S13 by using a filter screen, cleaning by using a detergent, and air-drying surface moisture at 20-25 ℃ after cleaning to prepare the gelatin microsphere with better comprehensive performance.
It is noted that, in the step S14, it is critical that the surface moisture is air-dried, and if the surface moisture of the gelatin microspheres is too much, they are adhered to each other, so that the ceramic hollow sphere with the double-shell structure cannot be obtained. Thus, the final effect of air drying the surface moisture is: controlling the water content of the cleaned gelatin microspheres to be 60-88%.
In the step S11, the gelatin solution with too high concentration may result in too large gelatin microspheres, poor dispersibility of the gelatin microspheres, and agglomeration and adhesion. Too low concentration of gelatin solution can also cause agglomeration and adhesion of gelatin microspheres, and large shrinkage after drying is not favorable for obtaining monodisperse gelatin microspheres. Therefore, the concentration of the gelatin solution is controlled to be 150-260 g/L.
In step S12, too large a stirring speed may result in too small a size of the gelatin ball; too little agitation results in too large a gelatin ball size and poor size uniformity. Therefore, the stirring speed is controlled to be 130 to 200 r/min.
In the step S12, the fact that the water-oil ratio of the soybean oil is too high means that the size of the gelatin ball is large, and the water-oil ratio is too low, so that the surface of the gelatin ball has partial concave and convex parts. Therefore, the water-oil ratio of the soybean oil is controlled to be 1/5-1/6.
In step S13, the formaldehyde solution with a mass concentration of 30% to 40% is used as the crosslinking agent because the gelatin microspheres prepared in this concentration range have smooth surfaces and are short in processing time.
Specifically, in the step S14, the prepared gelatin microspheres have uniform particle size and good roundness and dispersibility, and the roundness of the gelatin microspheres is 0.085-0.15; the gelatin microspheres have nearly spherical particle size, almost no adhesion between the gelatin microspheres and good dispersibility, so that when the mixed powder is scattered on the surfaces of the gelatin microspheres, the gelatin microspheres are dispersed, and the mixed powder can be wrapped on the surfaces of the gelatin microspheres more uniformly.
Specifically, in step 2, the ceramic raw material powder is one or more of alumina, silicon carbide, cordierite, mullite, zirconium dioxide, titanium dioxide, zinc oxide, aluminum nitride, boron nitride, silicon nitride, zirconium carbide, zirconium boride, hafnium carbide, titanium carbide, silicon oxide, calcium phosphate, hydroxyapatite or magnesium oxide, and preferably, the ceramic raw material powder is one or more of alumina, silicon carbide, cordierite or mullite.
In the step 2, the binder is one or more of sodium carboxymethylcellulose, hydroxypropyl methylcellulose, polyethylene glycol, polyvinyl alcohol or sodium polyacrylate. Preferably, the binder is hydroxypropyl methylcellulose or polyethylene glycol.
In the step 2, the sintering aid is one or more of titanium dioxide, magnesium oxide, silicon oxide, calcium carbonate, magnesium carbonate, mullite or low-melting-point glass powder. Preferably, the sintering aid is titanium dioxide or magnesium oxide.
Specifically, in step 2, in order to ensure that the obtained mixed powder is uniform, the ceramic raw material powder, the binder and the sintering aid are respectively and equally divided into a plurality of equal parts, each equal part is sequentially added into the container according to the sequence of the ceramic raw material powder, the sintering aid and the binder and is uniformly mixed, and the ceramic raw material powder, the sintering aid and the binder are added in batches according to the operation. Illustratively, the ceramic raw material powder, the sintering aid and the binder are respectively and equally divided into three equal parts, the first part is sequentially added into the container in the order of the first part of the ceramic raw material powder, the first part of the sintering aid and the first part of the binder and is uniformly mixed, the second part is sequentially added into the container in the order of the second part of the ceramic raw material powder, the second part of the sintering aid and the second part of the binder and is uniformly mixed, and the third part is sequentially added into the container in the order of the third part of the ceramic raw material powder, the third part of the sintering aid and the third part of the binder and is uniformly mixed to obtain mixed powder.
In the step 2, the mass ratio of the ceramic raw material powder to the sintering aid to the binder is 90-99.89: 0.1-9.9: 0.01-0.1.
In the step 2, the too high rotating speed of the pelletizing machine causes poor size uniformity of the composite balls, and the too low rotating speed causes powder on the surfaces of the composite balls to easily fall off, so that the rotating speed of the pelletizing machine is controlled to be 10-50 r/min.
In the step 2, when water is not sprayed in the pelletizing process, the powder on the surface of the pellets is easy to fall off due to overlong pelletizing time, and the powder on the surface of the pellets is not compact due to overlong time, so that the formation of a double-shell structure is influenced, and therefore, the pelletizing time is controlled to be 4-30 min.
In the step 2, when water is sprayed in the process of balling, the diameter of the composite ball can be gradually increased, and the balling time is controlled to be 0.5-2 h.
Specifically, in the step 3, the composite spheres are dried at 20-25 ℃ for 12-36 hours, because if the drying temperature is too high, the gelatin microspheres melt and the structure of the composite spheres collapses.
Specifically, in the step 3, the dried composite ball is placed into a high-temperature furnace to be sintered to prepare the ceramic hollow ball with the double-shell structure; the composite ball collapses due to excessive liquid phase generation caused by too high sintering temperature; the low sintering temperature can cause the low strength of the composite ball; therefore, the sintering temperature is controlled to be 1100-1550 ℃; in addition, the composite ball is easy to collapse due to too long sintering time, so that the sintering time is controlled to be 1-4 h.
Specifically, in the step 3, the ceramic hollow sphere with the double-shell structure is prepared after the composite sphere is sintered and naturally cooled to room temperature.
Compared with the prior art, the preparation method of the hollow ceramic ball with the double-shell structure, provided by the application, comprises the steps of firstly preparing the gelatin microsphere, then uniformly scattering the mixed powder on the surface of the gelatin microsphere for pelletizing, and finally drying and sintering the composite ball.
According to the method, the concentration, the stirring speed, the water-oil ratio and the concentration of the cross-linking agent of the gelatin solution are accurately controlled in the process of preparing the gelatin microspheres, and the gelatin microspheres with good roundness and dispersity and uniform size can be obtained.
In the process of preparing the composite balls, the composite balls with good roundness and dispersity and uniform size can be obtained by controlling the preparation method of the mixed powder, the proportion of the mixed powder, the rotating speed of the ball-making machine and the ball-making time.
This application is in the drying and sintering process of composite ball, and the structure of avoiding composite ball through control temperature and time collapses, finally obtains the ceramic hollow ball of the double shell structure that the size is even, the circularity is good, specific surface is high.
Example 1
Preparing a gelatin solution with the concentration of 260g/L, setting the stirring speed of a magnetic stirrer to be 150r/min, the water-oil ratio to be 1/5, the cross-linking agent to be a formaldehyde solution with the concentration of 37%, and the volume ratio of gelatin balls to the cross-linking agent to be 1/2; preparing gelatin microspheres with the diameter of 400-600 mu m and good roundness and dispersibility; air-drying the prepared gelatin microspheres at 20 ℃ for surface moisture, and putting the gelatin microspheres into a ball machine for preparing balls; weighing 99.49 mass ratio: 0.5: d of 0.0150Respectively dividing silicon carbide powder, mullite and hydroxypropyl methyl cellulose into three parts, sequentially adding the three parts into a container, uniformly mixing to obtain mixed powder, uniformly scattering the mixed powder onto the surface of a gelatin microsphere, starting a ball agglomerating machine to agglomerate, setting the rotating speed of the ball agglomerating machine to be 30r/min and the time to be 8min, and carrying out ball agglomerating to obtain the composite ball under the condition that water is not sprayed in the process of agglomerating; drying the composite ball at 20 ℃ for 24h, then placing the composite ball into a high-temperature furnace to sinter the composite ball at 1300 ℃, preserving the heat at the temperature for 2h, and naturally cooling the composite ball to room temperature to obtain the ceramic hollow ball with the double-shell structure, wherein the appearance of the sample at each stage in the embodiment is shown in fig. 1-6.
In the embodiment, the water content of the gelatin microspheres is 60-65%, the outer shell of the prepared hollow ceramic ball with the double-shell structure is 0.9-1.1 mm in outer diameter, the outer shell is 80-120 mu m in thickness, the inner shell is 0.51-0.72 mm in outer diameter, the inner shell is 70-100 mu m in thickness, and the density of the hollow ceramic ball is 0.4-0.55 g/cm3The roundness is 0.088 to 0.11, the porosity is 68 to 75 percent, and the specific surface area is 0.71 to 1.08m2/g。
Example 2
Preparing gelatin solution with concentration of 220g/L, setting stirring speed of magnetic stirrer at 180r/min, water-oil ratio at 1/5, and crosslinking agent at 35% formaldehyde solution, the volume ratio of gelatin balls to cross-linking agent is 1/3; preparing gelatin microspheres with the diameter of 310-; air-drying the prepared gelatin microspheres at 25 ℃ for surface moisture, and putting the gelatin microspheres into a ball machine for preparing balls; weighing the components in a mass ratio of 90: 8.98: 1: d of 0.0250The method comprises the following steps of (1) dividing the four raw materials into three parts respectively, sequentially adding the three parts into a container, uniformly mixing to obtain mixed powder, uniformly scattering the mixed powder onto the surface of a gelatin microsphere, starting a ball agglomerating machine to agglomerate, setting the rotating speed of the ball agglomerating machine to be 40r/min and the time to be 5min, and preparing a composite ball by agglomerating under the condition that water is not sprayed in the process of agglomerating; and drying the composite ball at 25 ℃ for 20h, then placing the composite ball into a high-temperature furnace to sinter at 1350 ℃, preserving the heat at the temperature for 2h, and naturally cooling to room temperature to obtain the silicon carbide ceramic hollow ball with the double-shell structure.
In the embodiment, the water content of the gelatin microspheres is 65-69%, the outer shell of the prepared ceramic hollow sphere with the double-shell structure is 0.72-1.08 mm in outer diameter, the outer shell is 78-117 microns in thickness, the inner shell is 0.45-0.66 mm in outer diameter, the inner shell is 48-70 microns in thickness, and the density of the ceramic hollow sphere is 0.38-0.58 g/cm3The roundness is 0.088 to 0.12, the porosity is 63 to 71 percent, and the specific surface area is 0.62 to 0.95m2/g。
Example 3
Preparing a gelatin solution with the concentration of 245g/L, setting the stirring speed of a magnetic stirrer to be 150r/min, the water-oil ratio to be 1/6, a cross-linking agent to be a 37% formaldehyde solution, and the volume ratio of gelatin balls to the cross-linking agent to be 1/5; preparing gelatin microspheres with the diameter of 350-580 mu m and good roundness and dispersibility; air-drying the prepared gelatin microspheres at 25 ℃ for surface moisture, and putting the gelatin microspheres into a ball machine for preparing balls; weighing 59 mass ratio: 39: 1.9: d of 0.15013.5 μm silicon carbide powder, d50Boehmite with the particle size of 3.5 mu m, magnesium oxide and sodium carboxymethylcellulose, respectively dividing the four raw materials into three parts, sequentially adding the three parts into a container, uniformly mixing to obtain mixed powder, uniformly scattering the mixed powder on the surface of the gelatin microsphere, starting a ball agglomerating machine to agglomerate, and setting the rotating speed of the ball agglomerating machine to be 40rThe/min and the time are 5min, and the composite ball is prepared by pelletizing under the condition that water is not sprayed in the pelletizing process; and drying the composite spheres at 25 ℃ for 20h, then placing the composite spheres into a high-temperature furnace to sinter at 1400 ℃, preserving the heat at the temperature for 2h, and naturally cooling to room temperature to obtain the silicon carbide-alumina composite ceramic hollow spheres with the double-shell structure.
In the embodiment, the water content of the gelatin microspheres is 68-75%, the outer shell of the prepared hollow ceramic ball with the double-shell structure is 0.76-1.15 mm in outer diameter, the outer shell is 85-102 mu m in thickness, the inner shell is 0.49-0.71 mm in outer diameter, the inner shell is 55-80 mu m in thickness, and the density of the hollow ceramic ball is 0.45-0.6 g/cm3The roundness is 0.086 to 0.12, the porosity is 75 to 83 percent, and the specific surface area is 3.2 to 5.9m2/g。
Example 4
Preparing a gelatin solution with the concentration of 150g/L, setting the stirring speed of a magnetic stirrer to be 145r/min, the water-oil ratio to be 1/6, the cross-linking agent to be a formaldehyde solution with the concentration of 37%, and the volume ratio of gelatin balls to the cross-linking agent to be 1/2; preparing gelatin microspheres with the diameter of 340-; air-drying the prepared gelatin microspheres at 25 ℃ for surface moisture, and putting the gelatin microspheres into a ball machine for preparing balls; weighing the components in a mass ratio of 95: 4.97: cordierite powder (d) of 0.035013.5 mu m), titanium dioxide and hydroxypropyl methyl cellulose, respectively dividing the three raw materials into three parts, sequentially adding the three parts into a container, uniformly mixing to obtain mixed powder, uniformly scattering the mixed powder on the surface of the gelatin microsphere, starting a ball agglomerating machine to agglomerate, setting the rotating speed of the ball agglomerating machine at 30r/min and the time of 4min, and agglomerating to obtain a composite ball under the condition that water is not sprayed in the process of agglomerating; and drying the composite ball at 25 ℃ for 20h, then placing the composite ball into a high-temperature furnace to be sintered at 1400 ℃, preserving the heat at the temperature for 2h, and naturally cooling to room temperature to obtain the double-shell structure cordierite ceramic hollow ball.
In the embodiment, the water content of the gelatin microspheres is 81-88%, the outer shell of the prepared hollow ceramic ball with the double-shell structure is 0.68-0.92 mm in outer diameter, the outer shell is 71-109 microns in thickness, the inner shell is 0.45-0.68 mm in outer diameter, the inner shell is 40-60 microns in thickness, and the hollow ceramic ball is made of gelatinThe density is 0.3 to 0.53g/cm3The roundness is 0.089 to 0.11, the porosity is 65 to 77 percent, and the specific surface area is 0.66 to 0.96m2/g。
Example 5
Preparing a gelatin solution with the concentration of 245g/L, setting the stirring speed of a magnetic stirrer to be 180r/min, the water-oil ratio to be 1/5, a cross-linking agent to be a 37% formaldehyde solution, and the volume ratio of gelatin balls to the cross-linking agent to be 1/4; preparing gelatin microspheres with the diameter of 330-; air-drying the prepared gelatin microspheres at 25 ℃ for surface moisture, and putting the gelatin microspheres into a ball machine for preparing balls; weighing the materials in a mass ratio of 98.99: 1: 0.01 part of alumina powder (d)504 mu m), magnesia powder and hydroxypropyl methyl cellulose, and the three raw materials are divided into three parts, sequentially added into a container and uniformly mixed to obtain mixed powder, and the mixed powder is uniformly scattered on the surface of the gelatin microsphere; setting the rotating speed of the ball forming machine to 35r/min and the time to 30min, and preparing the composite ball through ball forming under the condition that water is not sprayed in the ball forming process; and drying the composite ball at 25 ℃ for 20h, then placing the composite ball into a high-temperature furnace to be sintered at 1500 ℃, preserving the heat at the temperature for 2h, and naturally cooling to room temperature to obtain the alumina composite ceramic hollow ball with the double-shell structure.
In the embodiment, the water content of the gelatin microspheres is 68-75%, the outer shell of the prepared hollow ceramic ball with the double-shell structure is 1.0-1.2 mm in outer diameter, the outer shell is 74-115 mu m in thickness, the inner shell is 0.45-0.64 mm in outer diameter, the inner shell is 55-80 mu m in thickness, and the density of the hollow ceramic ball is 0.55-0.8 g/cm3The roundness is 0.085 to 0.103, the porosity is 70 to 80 percent, and the specific surface area is 0.82 to 1.25m2/g。
Comparative example 1
Comparative example 1 discloses single shell ceramic hollow spheres prepared by a conventional method from the ceramic raw powder of example 5. The external diameter of the single-shell ceramic hollow sphere is 1.0-1.2 mm, and the specific surface area is 0.46-0.75 m2The roundness is 0.084-0.17, and the porosity is 72-81%.
Comparative example 2
Comparative example 2 discloses the conventional method for preparing the ceramic raw powder of example 2The prepared single-shell ceramic hollow ball. The spherical outer diameter of the single-shell ceramic hollow sphere is 0.72-1.08 mm, and the specific surface area is 0.35-0.57 m2The roundness is 0.092-0.15, and the porosity is 64% -72%.
The table of comparative parameters of examples 1 to 5 and comparative examples 1 to 2 is shown in table 1 below, and it can be seen from table 1 that, for the ceramic hollow spheres having similar outer diameter and size ranges of the spheres obtained by different preparation methods using the same ceramic raw material powder, the specific surface area of the ceramic hollow sphere having the double-shell structure of the present application is significantly higher than that of the comparative examples, such as: in example 2 of the present application, the specific surface area is 0.62 to 0.95m when the outer diameter is 0.72 to 1.08mm2(g) when the outer diameter of comparative example 2 is 0.72 to 1.08mm, the specific surface area is 0.35 to 0.57m2(ii)/g; in example 5 of the present application, the specific surface area is 0.82 to 1.25m when the outer diameter is 1.0 to 1.2mm2(g) when the outer diameter of comparative example 1 is 1.0 to 1.2mm, the specific surface area is 0.46 to 0.75m2(ii)/g; for the field of catalysis, the larger the specific surface area is, the better the catalytic performance is, so that the ceramic hollow sphere with the double-shell structure has the obviously better catalytic performance; meanwhile, the ceramic hollow sphere prepared by the method is narrower in roundness distribution range, better in uniformity, larger in effective specific surface area and wider in application range when used as a catalyst.
TABLE 1 comparative table of relevant parameters for examples 1-5 and comparative examples 1-2
Figure BDA0002277689220000131
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims (8)

1. The preparation method of the ceramic hollow sphere with the double-shell structure is characterized by comprising the following steps of:
step 1, preparing gelatin microspheres;
step 2, putting the gelatin microspheres prepared in the step 1 into a ball forming machine, uniformly mixing ceramic raw material powder, a binder and a sintering aid to obtain mixed powder, uniformly scattering the mixed powder on the surfaces of the gelatin microspheres, and starting the ball forming machine to form balls to obtain composite balls with the surfaces of the gelatin microspheres uniformly coated with the mixed powder;
step 3, drying and sintering the composite ball to obtain a ceramic hollow ball with a double-shell structure; the ceramic hollow ball with the double-shell structure comprises an outer shell layer and an inner shell layer, wherein the outer shell layer is connected with the inner shell layer; a plurality of micropores are distributed on the outer shell layer and the inner shell layer;
the step 1 comprises the following steps:
s11, weighing gelatin, and dissolving the gelatin in water at 40-60 ℃ to obtain a gelatin solution; the concentration of the gelatin solution is 150-260 g/L;
step S12, dripping the prepared gelatin solution into soybean oil, and preparing gelatin balls through magnetic stirring; wherein the water-oil ratio of the soybean oil is 1/5-1/6;
step S13, putting the formed gelatin ball into a cross-linking agent for treatment;
s14, filtering the gelatin ball processed in the step S13 by using a filter screen, cleaning the gelatin ball by using a detergent, and air-drying surface moisture at 20-25 ℃ after cleaning to prepare gelatin microspheres; the water content of the cleaned gelatin microspheres is 60-88%;
in the step 3, drying the composite balls at the temperature of 20-25 ℃ for 12-36 h; the sintering temperature is 1100-1550 ℃, and the sintering time is 1-4 h.
2. The method according to claim 1, wherein in step S11, the concentration of the gelatin solution is 150-245 g/L.
3. The method according to claim 2, wherein in step S12, the stirring speed of the magnetic stirring is 130-200 r/min.
4. The method according to claim 1, wherein in the step 2, the ceramic raw material powder, the sintering aid and the binder are divided into equal parts, and each equal part is added to the container in the order of the ceramic raw material powder, the sintering aid and the binder and mixed uniformly.
5. The preparation method according to claim 1, wherein in the step 2, the rotation speed of the ball forming machine is 10 to 50 r/min.
6. The preparation method according to claim 1, wherein in the step 3, the composite spheres are dried at 20 to 25 ℃ for 20 to 36 hours.
7. The production method according to any one of claims 1 to 6, wherein in the step 3, the sintering temperature is 1100 to 1500 ℃.
8. The preparation method according to claim 7, wherein the specific surface area of the double-shell-structured ceramic hollow spheres is 0.62 to 5.9 m/g.
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