Study On Preparation Of Rare Earth Oxide Hollow Microspheres With Melamine-formaldehyde Microsphere As Template

In recent years, hollow shell materials with unique hollow structure has attracted widespread attention. Hollow nanosphere materials has been widely use in the drug carrier, biocatalysis, disease diagnosis, optoelectronic devices, and other fields due to its relatively low density, high specific surface area, good encapsulation ability, good permeability. The performance of rare earth elements together with the hollow structure of the nanoscale rare earth oxide hollow nanospheres, rare earth oxide hollow nanospheres have excellent optical, electrical, magnetic performance and hollow structure, so its application is more extensive.This paper use melamine and formaldehyde reaction in aqueous solution, formic acid as a catalyst, different particle size of yttrium oxide（Y₂O₃）, gadolinium oxide（Gd₂O₃） and ytterbium oxide（Yb₂O₃） hollownanospheres have been successfully prepared via a urea-based homogeneous precipitation technique with different particle size ofmelamine formaldehyde（MF） microspheres as templates. The effect of Template size and dosage of rare earth nitrat on the morphology of composite microspheres MF/RE（OH）CO₃（RE = Y, Gd, Yb）has been studied. The products microspheres were characterized by Fourier infrared spectrum（FT-IR）, thermo-gravimetric analysis（TG）,X-ray diffraction analysis（XRD）, laser particle size analysis（LPA）, X-ray photoelectron photoelectron spectroscopy（XPS）, scanning electron microscope（SEM）, transmission electron microscopy（TEM）, etc. The main research contents and results are as follows:1. The dosage of formic acid on the influence of MF microspheres morphology and particle size distribution was studied. The diameter of the MF spheres increase and the index of polydispersity first increase then decrease with the decrease of usage of the formic acid between 0.01-0.3 mL. And the size of MF spheres shows normal distribution.When the dosage of formic acid is 0.4 mL, the size of MF spheres is not uniform. When the usage of formic acid is 0.5 mL, can’t get MF spheres. When the dosage of formic acid is 0.03 mL, MF spheres with its polydispersity index is 0.129, the particle size is 2μm can be obtained. Study on the relationship between the amounts of formic acid andreaction rate.In the 0.01-0.06 mL range, with the increase of formic acid the reaction time shortened rapidly, the reaction rate accelerate. When the acid content is higher than 0.06 mL, with the increase of formic acid the reaction time shortened slowly, the reaction rate constant.2. Hollow shell structure MF/Y（OH）CO₃ composite microspheres with particle size is 2.2 μm have been prepared by a urea-based homogeneous precipitation technique with2 μm MF microspheres as templates, yttrium nitrate hexahydrate as raw materials.Calcination to remove tempaltes, the pherical morphology of Y₂O₃ hollow microspheres with a diameter of 1.6 μm was obtained. XRD results showed that the prepared Y₂O₃ hollow spheres is cubic phase. Studied the dosage of yttrium nitrate hexahydrate influence on composite microspheres morphology, the best coating process is determined.Template dosage is 0.2 g, yttrium nitrate hexahydrate is 0.8 mmol, getted the best effect of covering core-shell structure MF/Y（OH）CO₃ composite microspheres. The dosage of yttrium nitrate hexahydrate is 0.6 mmol 、 0.8 mmol 、 1.0 mmol, respectively, different coating layer thickness of MF/Y（OH）CO₃ composite microspheres can be obtained,calcination to remove the template, we can get patrticle size of 1.6 μm, shell thickness of Y₂O₃ hollow microspheres is 100 nm、150 nm、200 nm, respectively.3. Hollow shell structure MF/Gd（OH）CO₃ composite microspheres with particle size is 3.4 μm have been prepared by a urea-based homogeneous precipitation technique with 3 μm MF microspheres as templates, gadolinnium nitrate hexahydrate as raw materials. Calcination to remove tempaltes, the pherical morphology of Gd₂O₃ hollow microspheres with a diameter of 2.4 μm was obtained. XRD results showed that the prepared Gd₂O₃ hollow spheres is cubic phase. Studied the dosage of gadolinnium nitrate hexahydrate influence on composite microspheres morphology, the best coating process is determined. Template dosage is 0.2 g, gadolinnium nitrate hexahydrate is 0.7 mmol,getted the best effect of covering core-shell structure MF/Gd（OH）CO₃ composite microspheres. With 0.2 g diameter of 3 μm MF microspheres as template, change the dosage of gadolinnium nitrate hexahydrate is 0.7 mmol and 1.0 mmol, the particle size is2.4μm, shell thickness of Gd₂O₃ hollow microspheres is100 nm 、 200 nm, respectively.When gadolinnium nitrate hexahydrate is 1.0 mmol, the dosage of template is 0.2 g, the particle size of template is 2 μm 、 3 μm 、 4 μm, the particle size of MF/Gd（OH）CO₃composite microspheres is 2.4 μm、3.6 μm、4.8 μm. With the particle size increase, the morphology of composite microspheres become worse.4. Hollow shell structure MF/Yb（OH）CO₃ composite microspheres with particle size is 1.9 μm have been prepared by a urea-based homogeneous precipitation technique with 1.7 μm MF microspheres as templates, ytterbium nitrate pentahydrate as raw materials. Calcination to remove tempaltes, the pherical morphology of Yb₂O₃ hollow microspheres with a diameter of 1.5 μm was obtained. XRD results showed that the prepared Yb₂O₃ hollow spheres is cubic phase. Studied the dosage of ytterbium nitrate pentahydrate influence on composite microspheres morphology, the best coating process is determined. Template dosage is 0.2 g, the particle size is 1 μm、1.3 μm、1.7 μm、2 μm,ytterbium nitrate pentahydrate is 0.4 mmol、0.5 mmol、0.7 mmol、0.75 mmol, respectively,the best morphology of MF/Yb（OH）CO₃ composite microspheres can be getted.Calcination to remove tempaltes, the Yb₂O₃ hollow microspheres diameter is 1 μm、1.1μm、1.5 μm、1.8 μm. Sdudied the diameter of MF on the morphology of MF/Yb（OH）CO₃composite microspheres. When ytterbium nitrate pentahydrate is 0.8 mmol, the dosage of template is 0.1 g, the particle size of template is 1 μm、1.3 μm、1.7 μm、2 μm, prepared different morphology of MF/Yb（OH）CO₃ composite microspheres. The results show that the coating effect is poor when the template particle size less than 1.5 μm, the coating effect becomes better when the template size is higher than1.5 μm.