With Different Morphologies Of Cerium Oxide And Cerium - Si Composite Material Synthesis And The Nature Of Research

In our study, hexagonal nanoflake-like and short rod-like cerium oxides were synthesized by using a direct precipitation method and a homogeneous precipitation route, respectively. Then spheral and spindle-shaped cerium-silicon compounds were prepared through an in-situ method and a homogeneous precipitation route, respectively. In the process, we systematically researched the growth process of the cerium oxides and the cerium-silicon compounds and discussed the influence in their morphology, grain size and dispersion which were caused by changing the technology parameters. At the same time, we also discussed the properties of the as-prepared samples through a series of characterizations and analyzed their potential uses in the field of UV absorption, luminescent materials, catalytic carrier, polishing, etc.⑴In our study, we synthesized the hexagonal cerium oxide nano-flakes by using a surfactant-free route. The yellowish as-prepared sample whose mean grain size was about 30nm crystallized well. It also exhibited good dispersal. The method adopted greatly improved the defects of the traditional methods, such as the conglomeration caused by calcinations and the non-uniform grain size. Meanwhile, the method was very simple with low cost and the requirements to the equipment were not serious, so it was suitable for industrial production.⑵In this paper, the short rod-like cerium oxides were prepared through a homogeneous precipitation route with CTAB and F127 used as the surfactant. From TEM it could be seen that"the short rods"were composed of very small grains of cerium oxides whose size was about 10nm. And the short rods were jumbled up disorderly in the form of"cluster". We could also find that we could adjust the size of the short rods by changing the proportion of CTAB and F127. In our paper, monodisperse spindle-shaped cerium-silicon compounds were firstly synthesized by urea precipitation method and in-situ method with the surfactant of CTAB and F127. The use of CTAB made the compounds appear certain morphology while the doping of F127 solved the monodispersal of the compounds. So we can conclude that the functions of different surfactants are different. If they are mixed in a proper proportion, the morphologies of the products are likely to be controlled. For this aim, we provided the quotable experience and the reference data in the paper.⑶In our study, the spheral cerium-silicon compounds were firstly prepared through a in-situ method. The monodisperse spheres had a mean diameter of 0.9μm. From TEM it could be seen that there were some cerium oxide grains enchased on the surface of the spheres while other comparison experiments and characterization experiments could prove that the SiO2 hydrolyzed by TEOS combined the cerium oxide grains together and enwrapped them at last. In our research, we also firstly used the Raman spectrum technology to characterize the cerium-silicon compounds. From the results we can conclude that the presence of some defects such as lattice change or the low degree of crystallization, can involve relaxation of selection rules and then we can observe the blue-shift or red-shift.⑷In the process of preparing the cerium-silicon compounds, we firstly used the silane coupling agent (KH-570) to combine the ceric ions in the solution onto the surface of the silicon atoms. Silane coupling agent is often used to improve the surface properties of materials. In our research, KH-570 acted with the ceric ions and the silicon atoms, respectively, and finally formed the covalent bond. The thought of mixing the surfactant and silane coupling agent can also offer a route for how to control the morphologies of the products.⑸The as-prepared samples with different morphologies were proved to have the good theoretical and applied research values through the characterizations of UV-Vis, PL, BET, etc. So they were a kind of promising rare earth functional material. For example, they exhibited strong absorption and weak reflection to the UV lights, and showed the opposite properties to the visible lights. Meanwhile, they had specific morphologies and dispersed well, so they could be used as the UV absorbent in the glass of coating. The cerium oxide or cerium-silicon compound did not luminesce itself but transfer the absorbed energy to the avtivated centres which was due to their emission peaks were located at the forbidden band. So they also could be used as the basis substance of the phosphor. The specific surface of the spheral cerium-silicon compounds was large which could be used as the carrier of catalyst. In the aspect of polishing, if the spheral cerium-silicon compounds were taken as polishing powder, it could lower the cost on the premise of guaranteeing the polishing quality.