Rare earth oxides are widely used in magnetic materials, catalytic materials, hydrogen storage materials, optical glass, optical fiber and ceramic capacitors. Dysprosium oxide has excellent physical and chemical properties and is used as raw material for dysprosium metal, glass, additive for NdFeB permanent magnets, metal halogen lamps, magneto-optical memory materials, yttrium iron or yttrium aluminum garnet, and as control rods for nuclear power reactors in the atomic energy industry. With the development of science and technology, large specific surface nano dysprosium oxide demand more and more, when the particle size decreases to nanometer size, specific surface area increased surface effect, at the same time with quantum size effect and macroscopic quantum tunneling effect, become the basis for the development of special functional materials, such as in the porcelain fused apparatus, dysprosium oxide nanoparticles can significantly improve the performance of the product. Dysprosium oxide particle size obtained by mechanical grinding in the traditional preparation method, or the particle size precipitated by oxalic acid in the traditional rare earth industry method, is difficult to reach the nanometer size, and precipitation such as ammonia and ammonium bicarbonate is not conducive to environmental protection. In addition, the nano Dysprosium oxide obtained by other chemical methods is often poor in dispersion and prone to agglomeration. Chinese patent cn105502467a exposes a method of preparation of nano dysprosium oxide concrete steps as follows: according to take quality than 5% – 15% of polyethylene glycol (peg) 20000 surfactant stir in dysprosium nitrate in 15 to 30 min, then evenly mixing aging after add precipitant of sodium carbonate, the suction filter water, drain. Add surfactant n-butyl alcohol and calcination at 800 degrees after 3 to 5 h after 1 h of heat preservation for a quick dysprosium oxide nanoparticles; The precipitant in the patent is inorganic sodium carbonate, reaction speed is fast, and in order to control the reaction speed, the reaction material is added by dropping, the control is difficult, the cost is high, and the product quality difference between different reaction kettle is large, not suitable for industrial production. The purpose of the invention is to provide a method for preparing nano-sized dysprosium oxide with good dispersion and less agglomeration.
The technical scheme adopted in the invention to solve the above problems is: a method for preparing nano-sized dysprosium oxide, which comprises the following steps: (1) preparation of a solution of dysprosium nitrate with nitric acid. (2) Add the precipitant to the dispersant, mix evenly and add the deionized water, stir and dissolve. (3) Dysprosium nitrate solution in Step (1) and the solution obtained in Step (2) were mixed and stirred evenly, and then heated in a closed reactor for reaction. After the reaction, the temperature was lowered to 70℃, and then the pH was adjusted to 6.5~7.0. (4) Repeatedly wash the product obtained in Step (3) to centrifuge for dehydration, and then wash it with ethanol. (5) The products in step (4) are dried, and the dried products are crushed and screened with a grinder. (6) The sifted product in Step (5) is burned, and then crushed and sifted with a grinder to obtain nano-sized dysprosium oxide. Among them, the precipitant is alcohol amine precipitant, and the dispersant is composed of the following mass percentage components: polyvinyl alcohol 40-60%, polyethylene imine 10-30%, polyethylene pyrrolidone 10-30%, o-amino anisole 10-30%. The specific steps for preparing dysprosium nitrate solution described in Step (1) are as follows: adding dysprosium oxide to nitric acid to dissolve at room temperature to obtain a dysprosium nitrate solution with a concentration of 300~500g/ L. Preferably, the weight ratio of the precipitator to the dispersant described in Step (2) is 5 to 8:1. Preferably, the alcohol amine precipitant is diethanolamine. Optimally, the concentration of dysprosium nitrate described in Step (3) is 0.3~0.5 M, the concentration of precipitant is 0.7~0.9 M, and the weight ratio of dysprosium nitrate to precipitant is 1:1.5. Preferably, the temperature of the heating reaction described in Step (3) is 160℃ and the reaction time is 1~3h. Optimally, the number of water washing to centrifugal dehydration mentioned in Step (4) is 4-6 times, and the number of ethanol washing is 2-4 times. Preferably, the drying temperature described in Step (5) is 100~200℃ and the drying time is 3~6h.
The burning temperature described in Step (6) is 700~900℃ and the burning time is 2~5h. Compared with the existing technology, the advantages of this invention is that: (1) the invention adopts diethanolamine as precipitating agent, polyvinyl alcohol, polyethylene imine, polyvinylpyrrolidone, and a mixture of adjacent amino benzene methyl ether as the dispersant, preparation of dysprosium oxide nanoparticles stable uniform particle size, particle size range (20 to 50 nm) particle size, large surface area and good dispersibility, little reunion, can satisfy the MLCC miniaturization, high laminated ceramic capacitor, the demand for the development of high capacity. (2) The preparation method of nano-sized dysprosium oxide of the invention only needs to mix the reactants and react without dropping, and is easy to control, has the advantages of simple process, low cost, mild reaction and friendly to environment, and can be used for large-scale industrial production. (3) The ethanol washing after washing can effectively reduce agglomeration, improve dispersion, and stabilize particle size range.
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