Preparation Of Rare Earth Composite Nanomaterials And Study On Their Properties

Rare earth elements possess excellent physical and chemical properties, and have import applications in various felids of national economy and modem technology.China is a great nation in the respect of rare earth resource, and the researches and applications on rare earth composite materials are of vital important to the development of national economy.Nanometer materials are ultra-fine materials with the particle sizes of nanometer dimension (1-100nm),winch is between those of microscopic particles and macroscopic blocks.Nanometer materials possess lots of distinctive features different from traditional solid material,and have became the research hotspot of material science in recent years.Ammonium Perchlorate(AP)is the essential component of solid rocket propellant and the temperature of its thermal decomposition decides the combustion performance of the propellant.So the research of appropriate catalysts,in order to decrease the temperature of AP thermal decomposition,is of vital important to improve the property of solid rocket propellant.Rare earth photoluminescence complexes have the distinctive features of excellent fluorescence monochromaticity and high luminous intensity and attention is paid to them increasingly.However,their fluorescence stability is poor,and the fluorescence would become increasingly weaker under sunlight. To widen the application of rare earth photoluminescence complexes,that problem must be solved.Nanometer silica possesses the property of high purity,low density,high specific surface and high grade of transparency.If it covers the surface of rare earth photoluminescence complexes,the moisture and oxygen could be secluded from the complexes,so that the fluorescence stability of rare earth photoluminescence complexes is improved and yet its optical property won't be affected.In this paper,the neodymia/multi-walled carbon nanotube (Nd₂O₃/MWCNT),ceria/multi-walled carbon nanotube(CeO₂/MWCNT)and neodymium hydroxide/multi-walled carbon nanotube(La(OH)₃/MWCNT) composite materials and three rare earth oxide/ferric oxide/multi-walled carbon nanotube ternary composite materials were prepared by using chemical precipitation method.Nanometer Eu(TTA)₃phen/SiO₂ core/shell composite material was prepared by covering Eu(TTA)₃phen with SiO₂,using hydrolytic precipitation method.Transmission Electron Microscope(TEM),Scanning Electron Microscope(SEM),High Resolution Transmission Electron Microscope (HRTEM),X-Ray Diffraction(XRD),Infra-Red Absorption Spectra(FTIR) and X-Ray Photoelectron Spectroscopy(XPS)were adopted to characterize the appearances,structures and compositions of the products; Therrnogravimetry-Differential Thermal Analysis(TG-DTA)was adopted to research the catalytic performances of the carbon nanotube composites on AP thermal decomposition;photoluminescence spectrum(PL)and ultraviolet-visible spectrum(UV-vis)were adopted to research the photoluminescence and ultraviolet properties and fluorescence stability of Eu(TTA)₃phen/SiO₂.Firstly,Nd₂O₃/MWCNT composite material was prepared by using chemical precipitation method and the affection on AP thermal decomposition of the product acting as catalyst was researched.The experimental results showed that Nd₂O₃/MWCNT composite material can be successfully prepared by using chemical precipitation method.Nd₂O₃ and Nd(OH)₃ coexisted on the surface of Nd₂O₃/MWCNT,both of which possessed good crystallographic forms.Compared with nanometer Nd₂O₃,Nd₂O₃/MWCNT possessed better catalytic capability on AP thermal decomposition.The sampling methods of the experimental samples made a difference on the catalytic experiment results, and the best catalytic result appeared when de-ionized water served as the solvent of AP.The surface acid treatment on multi-walled carbon nanotubes and surfactant were key factors for the successfully preparation of Nd₂O₃/MWCNT composite material.In the reaction process,the Nd(OH)₃/MWCNT precursor was formed at first,and then Nd₂O₃/MWCNT was formed by calcination.Secondly,CeO₂/MWCNT and La(OH)₃/MWCNT composite materials were prepared by using chemical precipitation method and the affection on AP thermal decomposition of the products acting as catalyst was researched.The experimental results showed that CeO₂/MWCNT composite material can be successfully prepared by chemical precipitation method,while La₂O₃/MWCNT composite material can not be obtained by the method. CeO₂/MWCNT possessed a good crystallographic form and the average particle diameter of CeO₂ nanoparticles on its surface was about 9nm.The La(OH)₃ on the surface of La(OH)₃/MWCNT possessed poor crystallographic form and small particle size.Compared with La(OH)₃, La(OH)₃/MWCNT possessed better catalytic capability on AP thermal decomposition.Nanometer CeO₂ possessed no catalytic capability on AP thermal decomposition and the catalytic capability of CeO₂/MWCNTon AP thermal decomposition was from multi-walled carbon nanotube.Thirdly,Fe₂O₃/CeO₂/MWCNT,Fe₂O₃/Nd₂O₃/MWCNT and Fe₂O₃/Y₂O₃/MWCNT ternary composite materials were prepared by using chemical precipitation method and the affection on AP thermal decomposition of the products acting as catalyst was researched.The experimental results showed that Fe₂O₃/CeO₂/MWCNT,Fe₂O₃/Nd₂O₃/MWCNT and Fe₂O₃/Y₂O₃/MWCNT ternary composite materials can be successfully prepared by chemical precipitation method.The three ternary composite material possessed good crystallographic forms and the elements of Fe,Ce, Nd and Y existed in the forms ofα-Fe₂O₃,CeO₂,Nd₂O₃ and Y₂O₃ on the surface of multi-walled carbon nanotube.The sequence of catalytic capability of the three ternary composite materials on AP thermal decomposition was Fe₂O₃/Y₂O₃/MWCNT＞Fe₂O₃/CeO₂/MWCNT＞Fe₂O₃/Nd₂O₃/MWCNT,and each of them was better or approximate to that of their corresponding rare earth oxide/ferric oxide compound nanoparticle.Finally,nanometer Eu(TTA)₃phen/SiO₂ core/shell composite material was prepared by covering Eu(TTA)₃phen with SiO₂,using hydrolytic precipitation method.The experimental results showed the dosages of de-ionized water in the reactions decided the appearances of the products.The proportions between tetra ethyl ortho silicate and rare earth complex had important effect on fluorescence intensity of Eu(TTA)₃phen/SiO₂.The coating form of SiO₂ in Eu(TTA)₃phen/SiO₂ was physical coating.Thanks to Quantum Size Effect, compared to the ultraviolet absorption peak of Eu(TTA)₃phen,there was a blue shift in that of Eu(TTA)₃phen/SiO₂.Compared to Eu(TTA)₃phen,the fluorescence stability of Eu(TTA)₃phen/SiO₂ improved to a certain extent.In this paper,kinds of rare earth oxide/multi-walled carbon nanotube composite materials were prepared by using chemical precipitation method, controllable preparation basically realized,and the catalytic performances of the products on AP thermal decomposition were researched.Nanometer Eu(TTA)₃phen/SiO₂ core/shell composite material was prepared by using hydrolytic precipitation method,and its optical property was researched.The researches laid a theoretical basis for further applications.