CN109942015B - Freeze-drying preparation method of nano rare earth oxide powder - Google Patents
Freeze-drying preparation method of nano rare earth oxide powder Download PDFInfo
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Abstract
The invention provides a freeze-drying preparation method of nano rare earth oxide powder. Dissolving one or two of polyethylene glycol and fatty alcohol-polyoxyethylene ether serving as dispersing agents in water, dissolving soluble rare earth nitrate in water, and performing ultrasonic treatment to fully disperse and dissolve the rare earth nitrate; then spraying the solution into liquid nitrogen for pre-freezing or pre-freezing for more than 4 hours in a refrigerator at the temperature of below-20 ℃; when the temperature of the freeze dryer is reduced to below-50 ℃, putting the pre-frozen solution into the freeze dryer, starting a vacuum pump, maintaining the vacuum degree below 20Pa, and freeze-drying for 8-36 hours; after freeze-drying, grinding the composite powder, placing the powder in a furnace, and calcining the powder in the air to remove the dispersing agent to obtain the ultrafine nano rare earth oxide powder. The preparation method is a physical method, does not relate to chemical reaction, has little pollution and simple and convenient process. The average grain size of the prepared rare earth oxide powder reaches 10-50 nm, and the grain size distribution is extremely narrow.
Description
Technical Field
The invention provides a freeze-drying preparation method of nano rare earth oxide powder, belonging to the technical field of powder preparation engineering.
Background
The rare earth oxide has a plurality of unique spectral properties and physical and chemical properties, and is widely applied to the fields of petroleum, chemical industry, metallurgy, textile, ceramics, glass, permanent magnetic materials and the like. The rare earth oxide is widely applied to functional materials such as luminescent materials, magnetic materials, superconductors, high-performance ceramics, ultraviolet absorbers, precision polishing materials and the like. With the continuous progress of science and technology, the value of rare earth oxide will be greater and greater. The superfine rare earth oxide powder is an important component of rare earth nano material, and has great leap in performance on optical, electric, magnetic, mechanical and chemical characteristics due to the special physical and chemical properties.
At present, the preparation of the nano rare earth oxide powder mainly comprises a precipitation method and a hydrothermal method. In patent CN 105129834A "a method for preparing rare earth oxide with controllable granularity and narrow distribution", powder of 2.0 μm to nanometer level is prepared by precipitation method; in patent CN 105129834A "preparation method of nanometer rare earth oxide powder", 70nm powder is prepared by precipitation method; in patent CN 1150130C, "a method for preparing nano rare earth oxide powder", 100nm rare earth oxide powder is prepared by precipitation method; in patent CN 101665503A rare earth complex, rare earth oxide and preparation method thereof, the rare earth oxide powder with the particle size of 50 nm-1 μm is prepared by a hydrothermal method.
The precipitation method and the hydrothermal method for preparing the nano rare earth oxide powder generally involve chemical reactions, the reaction process is complicated, the reaction conditions are difficult to control accurately, and the reaction degree is difficult to carry out completely. Meanwhile, the nanometer yttrium oxide obtained by a chemical precipitation method and a hydrothermal method has the problem of larger crystal grains. In addition, the chemical precipitation method and the hydrothermal method are not suitable for mass production, the cost is high, both the chemical precipitation method and the hydrothermal method need a large amount of chemicals, the experimental period is long, and meanwhile, the hydrothermal method also needs long-time constant-temperature heating and consumes electric energy.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a freeze-drying preparation method of nano rare earth oxide powder.
The technical scheme of the invention is as follows:
dissolving one or two of polyethylene glycol and fatty alcohol-polyoxyethylene ether serving as dispersing agents and a soluble rare earth nitrate solution in water, performing ultrasonic treatment to fully disperse and dissolve the solution, pre-freezing the solution in a low-temperature environment, then putting the solution into a freeze dryer to freeze-dry powder, and finally calcining the powder in the air to obtain the nano rare earth oxide powder.
The specific technical scheme of the invention comprises the following steps:
(1) dissolving one or two of polyethylene glycol and fatty alcohol-polyoxyethylene ether serving as dispersing agents in water, dissolving soluble rare earth nitrate in water, and performing ultrasonic treatment to fully disperse and dissolve the rare earth nitrate;
(2) then spraying the solution into liquid nitrogen for pre-freezing or pre-freezing for more than 4 hours in a refrigerator at the temperature of below-20 ℃;
(3) when the temperature of the freeze dryer is reduced to below-50 ℃, putting the pre-frozen solution into the freeze dryer, starting a vacuum pump, maintaining the vacuum degree below 20Pa, and freeze-drying for 8-36 hours;
(4) after freeze-drying, grinding the composite powder, placing the powder in a furnace, and calcining the powder in the air to remove the dispersing agent to obtain the ultrafine nano rare earth oxide powder.
In the step (1), the rare earth nitrate is one of scandium salt, yttrium salt, lanthanum salt and cerium salt, and the concentration of the rare earth nitrate in the solution is 0.01-0.1 g/mL.
The mass of the dispersing agent in the step (1) is 2-10% of that of the rare earth nitrate; the power of ultrasonic treatment is 100-300W, and the ultrasonic treatment time is 0.3-1 h.
And (4) calcining at 400-800 ℃ for 0.5-2 h to remove the dispersant and obtain superfine nano rare earth oxide powder.
The freeze drying process is one physical process, and includes low temperature freezing of water inside material, and subsequent vacuum pumping to convert ice crystal into gaseous sublimation and to form solid grains after dewatering. After the dispersing agent polyethylene glycol (PEG) and fatty alcohol-polyoxyethylene ether (AE) are added, the dispersing agent and the rare earth salt are separated out together at the ice crystal boundary, an adsorption layer is formed on the surface of rare earth salt particles, which is equivalent to a film consisting of the dispersing agent, so that the charges on the surface of solid particles are increased, and the charges are mutually repelled due to the same charges, thereby improving the reaction force between the particles forming the three-dimensional obstruction, and further inhibiting the particle agglomeration in the solidification process. During the subsequent calcination, PEG or AE is removed to leave many voids, reducing the contact between grains, and the tendency of the rare earth oxide grains to grow is also reduced. The average grain size of the rare earth oxide powder prepared by a freeze drying method after the addition of the dispersing agent reaches 10-50 nm, the grain size distribution is extremely narrow, and the performance of subsequent materials is improved.
The invention has the advantages that:
1. compared with a chemical precipitation method and a hydrothermal method, the preparation method is a pure physical method, does not involve chemical reaction, has little pollution and simple and convenient process.
2. The preparation method can realize accurate regulation and control of the size, shape and distribution of crystal grains on the basis of ensuring purity and uniform doping, and has loose powder, less agglomeration and good dispersibility.
3. The invention can realize the preparation of the superfine nano rare earth oxide powder and is also very suitable for preparing a large amount of superfine nano rare earth oxide powder in a single batch.
Drawings
FIG. 1: example 1 XRD picture of ultrafine nano yttrium oxide powder prepared by freeze-drying method;
FIG. 2: example 1 TEM picture of ultra fine nano yttrium oxide powder prepared by freeze drying method;
FIG. 3: example 1 TEM pictures of ultra-fine nano yttrium oxide powders prepared by comparative experiments;
FIG. 4: example 2 TEM pictures of ultra-fine nano-yttria powder prepared by freeze-drying.
Detailed Description
The features of the present invention are further described below by way of examples, but the present invention is not limited to the following examples.
Example 1
(1) 0.1g of polyethylene glycol PEG is firstly dissolved in 100mL of deionized water, 2g of yttrium nitrate is dissolved in the deionized water, and finally the solution is added to 200mL (the concentration of yttrium nitrate is 0.01g/mL) with the deionized water and is fully dissolved and dispersed by ultrasonic treatment (the ultrasonic treatment power is 100W, and the ultrasonic time is 1 h).
(2) The solution was sprayed into liquid nitrogen for prefreezing.
(3) And after the temperature of the freeze dryer is reduced to reach the freezing temperature of minus 60 ℃ and is stabilized, putting the pre-frozen solution into the freeze dryer, starting a vacuum pump, maintaining the vacuum degree below 20Pa, and freeze-drying for 36 hours.
(4) And grinding the freeze-dried powder and calcining the powder in air at 500 ℃ for 1h to remove the dispersing agent, thus obtaining the superfine nano yttrium oxide powder. XRD is shown in figure 1, and the phase is pure yttrium oxide. Meanwhile, the average grain size of the superfine nano yttrium oxide powder is 14.7nm, and the surface appearance is shown in figure 2.
(5) To highlight the advantage of freeze-drying, a control experiment was set up. And (3) placing the solution obtained in the step (1) in a drying oven, keeping the temperature at a constant temperature of 60 ℃ for 24 hours, and calcining the obtained precursor powder according to the step (4). The obtained yttrium oxide powder has a grain size of 50-100nm and a surface morphology shown in FIG. 3. In contrast, the freeze-drying method has the advantages of extremely small crystal grains and extremely narrow granularity division of the powder.
Example 2
(1) 2g of polyethylene glycol PEG is firstly dissolved in 100mL of deionized water, 20g of yttrium nitrate is then dissolved in the deionized water, and finally the solution is added to 200mL (the concentration of yttrium nitrate is 0.1g/mL) with the deionized water and is fully dissolved and dispersed by ultrasonic treatment (the ultrasonic treatment power is 300W, and the ultrasonic time is 0.3 h).
(2) The solution was sprayed into liquid nitrogen for prefreezing.
(3) And after the temperature of the freeze dryer is reduced to reach the freezing temperature of minus 50 ℃ and is stabilized, putting the pre-frozen solution into the freeze dryer, starting a vacuum pump, maintaining the vacuum degree below 20Pa, and freeze-drying for 24 hours.
(4) And grinding the freeze-dried powder and calcining the powder in air at 500 ℃ for 1h to remove the dispersing agent, thus obtaining the superfine nano yttrium oxide powder. The average grain size of the superfine nano yttrium oxide powder is 35.4nm, and the surface appearance is shown in figure 4. The powder prepared by the freeze drying method has pure phase, extremely small crystal grains and extremely narrow granularity division, and the method has remarkable advantages.
Example 3
(1) Firstly, 0.02g of fatty alcohol-polyoxyethylene ether AE is dissolved in 100mL of deionized water, then 10g of scandium nitrate is dissolved in the deionized water, finally the solution is added to 200mL (the concentration of the scandium nitrate is 0.05g/mL) by the deionized water, and the solution is fully dissolved and dispersed by ultrasonic treatment (the ultrasonic treatment power is 200W, and the ultrasonic time is 0.5 h).
(2) The solution was sprayed into liquid nitrogen for prefreezing.
(3) And after the temperature of the freeze dryer is reduced to reach the freezing temperature of minus 50 ℃ and is stabilized, putting the pre-frozen solution into the freeze dryer, starting a vacuum pump, maintaining the vacuum degree below 20Pa, and freeze-drying for 24 hours.
(4) And grinding the freeze-dried powder and calcining the powder in air at 800 ℃ for 0.5h to remove the dispersing agent, thus obtaining the superfine nano scandium oxide powder. The average grain size of the superfine nano scandium oxide powder is 75.4 nm. The powder prepared by the freeze drying method has pure phase, extremely small crystal grains and extremely narrow granularity division, and the method has remarkable advantages.
Example 4
(1) 0.1g of polyethylene glycol PEG and 0.1g of fatty alcohol-polyoxyethylene ether AE are dissolved in 100mL of deionized water, 10g of lanthanum nitrate is dissolved in the deionized water, the solution is added to 200mL (the concentration of the lanthanum nitrate is 0.05g/mL) with the deionized water, and the solution is subjected to ultrasonic treatment (the ultrasonic treatment power is 200W, and the ultrasonic treatment time is 0.5h) to be fully dissolved and dispersed.
(2) The solution was pre-frozen in a refrigerator at-20 ℃ for 4 h.
(3) And after the temperature of the freeze dryer is reduced to reach the freezing temperature of minus 60 ℃ and is stabilized, putting the pre-frozen solution into the freeze dryer, starting a vacuum pump, maintaining the vacuum degree below 20Pa, and freeze-drying for 24 hours.
(4) And grinding the freeze-dried powder and calcining the powder in air at 400 ℃ for 2h to remove the dispersant, thus obtaining the superfine nano lanthanum oxide powder. The average grain size of the superfine nano lanthanum oxide powder is 13.4 nm. The powder prepared by the freeze drying method has pure phase, extremely small crystal grains and extremely narrow granularity division, and the method has remarkable advantages.
Example 5
(1) 0.1g of polyethylene glycol PEG is firstly dissolved in 20mL of deionized water, 2g of cerous nitrate is then dissolved in the deionized water, and finally the solution is added to 20mL (the concentration of AMT is 0.05g/mL) with the deionized water and is fully dissolved and dispersed by ultrasonic treatment (the ultrasonic treatment power is 200W, and the ultrasonic time is 0.5 h).
(2) The solution was pre-frozen in a refrigerator at-30 ℃ for 6 h.
(3) And after the temperature of the freeze dryer is reduced to reach freezing temperature of-70 ℃ and is stabilized, putting the pre-frozen solution into the freeze dryer, starting a vacuum pump, maintaining the vacuum degree below 10Pa, and freeze-drying for 8 hours.
(4) And grinding the freeze-dried powder and calcining the powder in air at 500 ℃ for 0.5h to remove the dispersing agent, thus obtaining the superfine nano yttrium oxide cerium powder. The average grain size of the superfine nano cerium oxide powder is 40.4 nm. The powder prepared by the freeze drying method has pure phase, extremely small crystal grains and extremely narrow granularity division, and the method has remarkable advantages.
Although the method and the preparation technique of the present invention have been described by way of preferred embodiments, it is obvious to those skilled in the art that the method and the preparation technique described herein can be modified or recombined to realize the final preparation technique without departing from the content, spirit and scope of the present invention. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and content of the invention.
Claims (1)
1. A freeze-drying preparation method of nano rare earth oxide powder is characterized by comprising the following steps:
(1) dissolving one or two of polyethylene glycol or fatty alcohol-polyoxyethylene ether serving as a dispersing agent in water, dissolving soluble rare earth nitrate in the water, and performing ultrasonic treatment to fully disperse and dissolve the rare earth nitrate;
(2) pre-freezing the solution in a low-temperature environment, and then putting the solution into a freeze dryer to freeze-dry powder;
(3) finally, grinding the freeze-dried powder and calcining the powder in the air to obtain superfine rare earth oxide powder;
the rare earth nitrate in the step (1) is one of scandium salt, yttrium salt, lanthanum salt and cerium salt, and the concentration of the rare earth nitrate in the solution is 0.01-0.1 g/mL;
the mass of the dispersant in the step (1) is 2-10% of that of the rare earth nitrate; the power of ultrasonic treatment is 100-300W, and the ultrasonic treatment time is 0.3-1 h;
spraying the solution into liquid nitrogen for prefreezing;
after the temperature of the freeze dryer is reduced to-70 ℃ or below, putting the pre-frozen solution into the freeze dryer, opening a vacuum pump, freeze-drying for 8-36 hours, and maintaining the vacuum degree below 20 Pa;
and (3) calcining at 500-800 ℃ for 0.5-2 h to remove the dispersant and obtain superfine nano rare earth oxide powder.
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