CN107840356B - Method for improving dispersibility of prepared oxide powder by vacuum freeze drying - Google Patents
Method for improving dispersibility of prepared oxide powder by vacuum freeze drying Download PDFInfo
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- CN107840356B CN107840356B CN201710886257.5A CN201710886257A CN107840356B CN 107840356 B CN107840356 B CN 107840356B CN 201710886257 A CN201710886257 A CN 201710886257A CN 107840356 B CN107840356 B CN 107840356B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/021—After-treatment of oxides or hydroxides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/20—Compounds containing only rare earth metals as the metal element
- C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G25/00—Compounds of zirconium
- C01G25/02—Oxides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
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Abstract
The invention belongs to the technical field of nano powder preparation and application, and particularly relates to a method for improving the dispersibility of prepared oxide powder by vacuum freeze drying. The nucleation of the precipitate gel is connected with the agglomeration phenomenon generated in the calcining process, the ammonium sulfate added in the suction filtration process can be firmly adsorbed on the surface of the metal cation, the phenomenon that the dispersing agent added in the precipitation process is washed away by deionized water without adding ammonium sulfate is avoided, and then the precursor gel is subjected to sublimation drying by a vacuum freeze drying method. The added ammonium sulfate is filtered and filtered, and the ammonium sulfate is frozen and dried in vacuum, so that the agglomeration phenomenon of the nano powder can be effectively avoided in the subsequent high-temperature powder calcining process.
Description
Technical Field
The invention belongs to the technical field of nano powder preparation and application, and particularly relates to a method for improving the dispersibility of prepared oxide powder through vacuum freeze drying.
Background
The nano powder has the characteristics of small size, large specific surface area, large surface atomic ratio, large surface energy, increased interface disorder and the like, so that the nano powder generates a plurality of excellent performances and new effects compared with the traditional material, such as quantum size effect, small size effect, surface effect, macroscopic quantum tunneling effect and the like. However, the nano powder has high sintering activity and large surface energy, so that the energy is in an unstable state, and the nano powder is easy to agglomerate, thereby destroying the superfine property and uniformity of the nano powder, increasing the particle size, losing the unique characteristics of the nano powder, seriously affecting the performance of the nano material, and reducing the thermal property, optical property, electrical property and magnetic property of the material, so that the generation and existence of the agglomeration state should be reduced as much as possible in the process of preparing the nano powder.
The chemical precipitation method can accurately control the proportion of each reaction component and can obviously improve the sintering activity of the powder, so the chemical precipitation method is a common method for preparing the nano powder at present. However, this method is liable to cause a serious agglomeration phenomenon of the powder. A large number of studies have confirmed that, in the whole process of preparing nano powder by chemical precipitation, each process may cause agglomeration of the powder from the configuration of raw materials, the reaction nucleation process, the washing, drying and calcining of precursors. But this advantage is greatly diminished when agglomerates are produced. Therefore, the agglomeration problem in the present nanomaterial preparation process is now a hot problem that is researched and solved by more and more people in the industry.
The agglomeration of powder can be generally divided into two forms, namely soft agglomerates and hard agglomerates. Soft agglomeration is mainly caused by electrostatic and van der waals forces between particles or capillary forces due to the presence of liquid within the agglomerate, with small interaction forces; the formation of hard agglomerates, in addition to electrostatic and van der waals forces, also involves chemical bonding and strong bonding of liquid or solid phase bridges between particles, and such agglomerates have a large interaction force and high strength. Vacuum Freeze Drying (VFD) is a new method for directly removing water from solution, sol or gel to prepare superfine powder with small particle size, less agglomeration and uniform dispersion. The vacuum freeze-dried material has porosity, instant solubility and rehydration property due to the existence of sublimed moisture space, and has large specific surface area and high pore volume; soluble substances dissolved in water are separated out on site in the sublimation process, and inorganic salt dissolved in water is uniformly present, so that the agglomeration phenomenon caused by the migration of water in the material to the surface in the common oven drying method is avoided, and the method is widely applied to the industries of materials, medicines and the like. However, the dispersant such as ammonium sulfate added in the reaction process of the traditional chemical precipitation method can be cleaned in the suction filtration process, so that the vacuum freeze-drying method only improves certain dispersibility in the step of precursor gel drying, and actually, the dried precursor powder still can spontaneously generate agglomeration phenomenon during natural storage due to larger surface energy and the added dispersant. In addition, because the dispersant is largely washed away in the suction filtration stage, the precursor still generates a large amount of agglomeration after being calcined, so that the nano powder is largely sintered, and the activity of the powder is reduced. Thus, there is a need for improvements and enhancements to the prior art.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a method for improving the dispersibility of the prepared oxide powder by vacuum freeze drying, ammonium sulfate is added in the suction filtration process to be firmly adsorbed on the surface of metal cations, the phenomenon that a dispersing agent added in the precipitation process is washed away by deionized water without adding ammonium sulfate is avoided, and then precursor gel is subjected to sublimation drying by a vacuum freeze drying method. The added ammonium sulfate is filtered and filtered, and the ammonium sulfate is frozen and dried in vacuum, so that the agglomeration phenomenon of the nano powder can be effectively avoided in the subsequent high-temperature powder calcining process.
The problem of agglomeration generated in the drying and calcining processes of the superfine powder can be effectively solved, the dispersibility of the superfine oxide powder is improved, and the particle size distribution of the powder is more uniform.
The technical scheme of the invention is as follows: a method for improving the dispersibility of oxide powder by vacuum freeze drying. The method is characterized in that: combining the processes of suction filtration and drying, carrying out suction filtration by using deionized water added with a dispersing agent in the stage of suction filtration, and then carrying out vacuum freeze drying, wherein the method comprises the following specific steps:
1) carrying out suction filtration on a precipitation precursor prepared by a chemical precipitation method by using deionized water containing a dispersing agent, wherein the dispersing agent is ammonium sulfate, and the molar ratio n (SO) of the ammonium sulfate to raw material metal ions4 2-) N (M) is 5-30%, M is metal ion Al3+、Y3+、Zr4+One of (1); preparing the filtered precursor filter cake into a paste with the concentration of 0.05-1 mol/L by using deionized water, then containing the paste by using a container, placing the paste in a vacuum freeze dryer, cooling to a target temperature, preserving the temperature and keeping a constant vacuum degree, and carrying out sublimation drying after the heat preservation is finished to obtain precursor powder with good dispersity;
2) and calcining the freeze-dried precursor at high temperature by a muffle furnace to obtain the inorganic functional nano powder with good dispersibility.
Further, in the drying method, the paste in the step 1) is contained in a container with the same loading amount every time, but the thickness is set to be 2-10 mm.
Further, in the drying method, the cooling rate in the step 1) is 0.5-5 ℃/min.
Further, in the above drying method, the target temperature in the step 1) is set to-60 to-30 ℃.
Further, in the drying method, the vacuum degree in the step 1) is 1-20 Pa.
Further, in the drying method, the heat preservation time in the step 1) is set to be 10-40 h.
Further, in the drying method, the oxide powder prepared in the step 2) has good dispersibility, the average particle size is 100-250 nm, and the agglomeration coefficient is 5-8.
The invention has the beneficial technical effects
According to the method for improving the dispersibility of the oxide powder prepared by the chemical precipitation method, deionized water added with a dispersing agent is used for carrying out suction filtration in the suction filtration stage, the nucleation of precipitate gel is connected with the agglomeration phenomenon generated in the calcination process, ammonium sulfate added in the suction filtration process can be firmly adsorbed on the surface of metal cations, the dispersing agent added in the precipitation process is prevented from being washed away by deionized water without adding ammonium sulfate, and then the precursor gel is subjected to sublimation drying by a vacuum freeze-drying method. The added ammonium sulfate is filtered and filtered, and the ammonium sulfate is frozen and dried in vacuum, so that the agglomeration phenomenon of the nano powder can be effectively avoided in the subsequent high-temperature powder calcining process. Therefore, the following advantages are provided:
1) the method is simple and convenient to operate, can be used for improving the dispersibility of the oxide powder prepared by a general chemical precipitation method, is particularly suitable for the precursor prepared under a water system condition, and improves the dispersibility of the precursor.
2) The dispersing agent is added in the suction filtration process, so that the phenomenon that the dispersing agent added in the particle nucleation process is washed away in the suction filtration stage is avoided, and the agglomeration phenomenon of the precursor is greatly reduced.
3) The method avoids the use of complex instruments and harmful chemical reagents, greatly reduces the treatment cost and has positive significance for environmental protection.
4) The oxide powder treated by the method has good dispersibility, particle size uniformity and extremely high sphericity, and can completely improve the thermal property, optical property, electrical property, magnetism property and other properties of the nano material.
Description of the drawings:
FIG. 1 shows Al prepared by chemical precipitation method without adding ammonium sulfate, washed and dried in the process of suction filtration2O3SEM image of precursor.
FIG. 2 shows Al prepared by chemical precipitation method and washed without adding ammonium sulfate in the suction filtration process2O3SEM images of the precursors after calcination.
FIG. 3 shows Al prepared by chemical precipitation2O3SEM images of precursors after improved dispersibility using the present invention. FIG. 4 shows Al prepared by chemical precipitation2O3The precursor adopts an SEM picture of calcining after improving the dispersibility.
The specific implementation mode is as follows:
the process of the present invention is further illustrated below with reference to examples. It should be understood that these examples are illustrative of the invention only and are not intended to limit the scope of the invention. Further, it should be understood that various changes and modifications of the present invention may be made by those skilled in the art after reading the teachings of the present invention, and such equivalents are also within the scope of the present invention as defined in the appended claims.
Example 1
A method for improving the dispersibility of oxide powder by vacuum freeze drying. The following steps are carried out in sequence:
1) adding n (SO) into the precipitation precursor prepared by chemical precipitation4 2-):n(Al3+) Deionized water as dispersant, 0% ammonium sulfate by mole was suction filtered.Preparing the filtered precursor filter cake into a 'paste' with the concentration of 0.05mol/L by using deionized water, then placing the paste into a culture dish, controlling the thickness of the paste to be 3mm, and placing the paste into a vacuum freeze dryer to be reduced to-60 ℃ at the cooling rate of 1 ℃/min. Keeping the temperature for 10h, and then carrying out sublimation drying to obtain precursor powder with good dispersibility
2) Calcining the freeze-dried precursor at high temperature in a muffle furnace to obtain Al with uniform particle size distribution, average particle size of 300nm, agglomeration coefficient of 12 and slightly poor dispersibility2O3Nano powder; al (Al)2O3SEM picture of precursor shown in figure 1, Al2O3The SEM of the calcined precursor is shown in figure 2.
Example 2
A method for improving the dispersibility of oxide powder by vacuum freeze drying. The following steps are carried out in sequence:
1) adding n (SO) into the precipitation precursor prepared by chemical precipitation4 2-):n(Al3+) Deionized water as dispersant, 5% ammonium sulfate by mole was suction filtered. Preparing the filtered precursor filter cake into a 'paste' with the concentration of 0.05mol/L by using deionized water, then placing the paste into a culture dish, controlling the thickness of the paste to be 3mm, and placing the paste into a vacuum freeze dryer to be reduced to-60 ℃ at the cooling rate of 1 ℃/min. Keeping the temperature for 10h, and then carrying out sublimation drying to obtain precursor powder with good dispersibility
2) Calcining the freeze-dried precursor at high temperature in a muffle furnace to obtain Al with uniform particle size distribution, average particle size of 120nm, agglomeration coefficient of 7 and good dispersibility2O3Nanopowder of Al2O3SEM image of precursor shown in figure 3, Al2O3The SEM of the calcined precursor is shown in figure 4.
Example 3
A method for improving the dispersibility of oxide powder by vacuum freeze drying. The following steps are carried out in sequence:
1) adding n (SO) into the precipitation precursor prepared by chemical precipitation4 2-):n(Y3+) Deionization of 7 mol% ammonium sulfate as dispersantAnd (5) carrying out suction filtration on the water. Preparing the filtered precursor filter cake into a 'paste' with the concentration of 0.2mol/L by using deionized water, then placing the paste into a culture dish, controlling the thickness of the paste to be 5mm, and placing the paste into a vacuum freeze dryer to be reduced to-55 ℃ at the cooling rate of 2 ℃/min. And after the heat preservation is finished for 12h, carrying out sublimation drying to obtain precursor powder with better dispersibility.
2) And calcining the freeze-dried precursor at high temperature by a muffle furnace to obtain the inorganic functional nano powder with uniform particle size distribution, average particle size of 180nm and agglomeration coefficient of 5 and good dispersibility.
Example 4
A method for improving the dispersibility of oxide powder by vacuum freeze drying. The following steps are carried out in sequence:
1) adding n (SO) into the precipitation precursor prepared by chemical precipitation4 2-):n(Y3+) Deionized water as dispersant, ammonium sulfate 20% molar ratio was suction filtered. Preparing the filtered precursor filter cake into paste with the concentration of 1mol/L by using deionized water, then placing the paste into a culture dish, controlling the thickness of the paste to be 6mm, and placing the paste into a vacuum freeze dryer to be reduced to-50 ℃ at the cooling rate of 3 ℃/min. And after the heat preservation is finished for 15h, sublimating and drying to obtain precursor powder with better dispersibility.
2) And calcining the freeze-dried precursor at high temperature by a muffle furnace to obtain the inorganic functional nano powder with uniform particle size distribution, average particle size of 220nm and agglomeration coefficient of 8 and good dispersibility.
Example 5
A method for improving the dispersibility of oxide powder by vacuum freeze drying. The following steps are carried out in sequence:
1) adding n (SO) into the precipitation precursor prepared by chemical precipitation4 2-):n(Zr4+) Deionized water as dispersant, ammonium sulfate 15% molar ratio was suction filtered. Preparing the filtered precursor filter cake into a 'paste' with the concentration of 0.3mol/L by using deionized water, then placing the paste into a culture dish, controlling the thickness of the paste to be 8mm, and placing the paste into a vacuum freeze dryer to be reduced to-30 ℃ at the cooling rate of 4 ℃/min. Health-care productAnd after the temperature is raised for 30h, sublimating and drying to obtain precursor powder with better dispersibility.
2) And calcining the freeze-dried precursor at high temperature by a muffle furnace to obtain the inorganic functional nano powder with uniform particle size distribution, average particle size of 230nm and agglomeration coefficient of 6.8 and good dispersibility.
Example 6
A method for improving the dispersibility of oxide powder by vacuum freeze drying. The following steps are carried out in sequence:
1) adding n (SO) into the precipitation precursor prepared by chemical precipitation4 2-):n(Zr4+) Deionized water as dispersant, 25% ammonium sulfate by mole was suction filtered. Preparing the filtered precursor filter cake into paste with the concentration of 0.8mol/L by using deionized water, then placing the paste into a culture dish, controlling the thickness of the paste to be 10mm, and placing the paste into a vacuum freeze dryer to be reduced to-40 ℃ at the cooling rate of 5 ℃/min. And after the heat preservation is finished for 35 hours, carrying out sublimation drying to obtain precursor powder with good dispersibility.
2) And calcining the freeze-dried precursor at high temperature by a muffle furnace to obtain the inorganic functional nano powder with uniform particle size distribution, average particle size of 150nm and agglomeration coefficient of 6 and good dispersibility.
Example 7
A method for improving the dispersibility of oxide powder by vacuum freeze drying. The following steps are carried out in sequence:
1) adding n (SO) into the precipitation precursor prepared by chemical precipitation4 2-):n(Zr4+) Deionized water as dispersant, ammonium sulfate 30% molar ratio was suction filtered. Preparing the filtered precursor filter cake into paste with the concentration of 1mol/L by using deionized water, then placing the paste into a culture dish, controlling the thickness of the paste to be 10mm, and placing the paste into a vacuum freeze dryer to be reduced to-40 ℃ at the cooling rate of 5 ℃/min. And after the heat preservation is finished for 40h, carrying out sublimation drying to obtain precursor powder with good dispersibility.
2) And calcining the freeze-dried precursor at high temperature by a muffle furnace to obtain the inorganic functional nano powder with uniform particle size distribution, average particle size of 160nm and good dispersity with agglomeration coefficient of 7.
Claims (5)
1. A method for improving the dispersibility of oxide powder by vacuum freeze drying is characterized in that: combining the processes of suction filtration and drying, carrying out suction filtration by using deionized water added with a dispersing agent in the stage of suction filtration, and then carrying out vacuum freeze drying, wherein the method comprises the following specific steps:
1) carrying out suction filtration on a precipitation precursor prepared by a chemical precipitation method by using deionized water containing a dispersing agent, wherein the dispersing agent is ammonium sulfate, and the molar ratio n (SO) of the ammonium sulfate to raw material metal ions4 2-) N (M) is 5-30%, M is metal ion Al3 +、Y3+、Zr4+One of (1); preparing the filtered precursor filter cake into a paste with the concentration of 0.05-1 mol/L by using deionized water, then containing the paste by using a container, placing the paste in a vacuum freeze dryer, cooling to a target temperature, preserving the temperature and keeping a constant vacuum degree, and carrying out sublimation drying after the heat preservation is finished to obtain precursor powder with good dispersity;
2) calcining the freeze-dried precursor at high temperature in a muffle furnace to obtain inorganic functional nano powder with good dispersibility; the calcined oxide powder has good dispersibility, the average particle size is 100-250 nm, and the agglomeration coefficient is 5-8;
the loading amount of the paste in the step 1) is kept the same when the paste is contained in a container, but the thickness is set to be 2-10 mm.
2. The preparation method according to claim 1, wherein the temperature reduction rate in step 1) is 0.5-5 ℃/min.
3. The production method according to claim 1, wherein the target temperature in step 1) is set to-60 to-30 ℃.
4. The method according to claim 1, wherein the degree of vacuum in the step 1) is 1 to 20 Pa.
5. The preparation method according to claim 1, wherein the holding time in step 1) is set to 10 to 40 hours.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103450475A (en) * | 2013-09-13 | 2013-12-18 | 中北大学 | Method for preparing core-shell structured conductive polyaniline/Co3O4 powder |
| CN106977206A (en) * | 2017-02-22 | 2017-07-25 | 江苏师范大学 | Spraying codepostion prepares the continuation method of high dispersancy nano oxide powder |
| CN107117586A (en) * | 2017-04-25 | 2017-09-01 | 江苏师范大学 | It is a kind of to improve the method that chemical precipitation method prepares oxide powder dispersiveness |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103450475A (en) * | 2013-09-13 | 2013-12-18 | 中北大学 | Method for preparing core-shell structured conductive polyaniline/Co3O4 powder |
| CN106977206A (en) * | 2017-02-22 | 2017-07-25 | 江苏师范大学 | Spraying codepostion prepares the continuation method of high dispersancy nano oxide powder |
| CN107117586A (en) * | 2017-04-25 | 2017-09-01 | 江苏师范大学 | It is a kind of to improve the method that chemical precipitation method prepares oxide powder dispersiveness |
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