Study On Preparation, Properties And Molding Of Multi-walled Carbon Nanotubes/rare Earth Oxide High Temperature Sensitive Fluorescent Nano-material

Carbon nanotubes （CNTs） were attracted by chemists, physics, biologists andmaterials scientists over the past decades, and become one of the most popularnanomaterials nowdays, due to their unique tubular structure and excellent electrical,mechanical, optical, thermal and other properties. CNTs can be removed under thehigh temperature calcination, therefore, they can also be the excellent templates forpreparation of nano-tubular material.The rare earth oxides with excellent photophysical properties are widely used inoptical devices. Our experiments indicate that: CNTs themselves have fluorescence,but they have a strong fluorescence quenching effect on the rare earth oxides. In orderto make full use of the fluorescence quenching effect of the CNTs, at first we preparedCNTs/rare earth oxide complexes that exhibit very weak emission, then graduallyremove CNTs template under the high temperature calcination, using scanningelectron microscopy （SEM） analysis, transmission electron microscopy （TEM） andenergy dispersive spctral （EDS） analysis showed that the rare earth oxide nanotubeswere formed, and the fluorescence intensity of the complex gradually increased withthe increasing of calcination temperature. Therefore, this material exhibit a stronghigh temperature sensitive fluorescence, making it have potential applications in hightemperature warning materials, sensors and field emission displays, and so on. In thisstudy, the strong fluorescence quenching effect of the CNTs and the strongfluorescence of rare earth oxides were applied fully, then, two were composited, andunder high temperature calcination strongly fluorescent rare earth oxides nanotubeswere formed, CNTs/rare earth oxides nanocomposites performed strong hightemperature sensitive fluorescence. Firstly, the purification and functionalization ofCNTs were discussed; then by precipitation method, carbon nanotubes/rare earthhydroxide complexes were prepared, the ratio of carbon nanotubes and rare-earthprecursor, surfactant type and dosage, pH value and other factors were explored onthe orthogonal experiments, then under high temperature calcination CNTs/rare earthoxides nanocomposites were prepared, the combustion completely of CNTs andcalcination temperature on the fluorescence intensity of the complex were discussed, and the mechanism that the fluorescent intensities of emission bands increase with theincreasing of calcination temperature was discussed; finally calcined strongfluorescent substance was filmed, the main contents and conclusions are as follows:Firstly, on the basis of previously explored the processing technology of CNTs inthe laboratory, the CNTs were had further modification, using aqua regia, mixed acid（the volume ratio of concentrated H₂SO₄and concentrated HNO₃=3:1）, and surfactant（sodium dodecyl benzene sulfonate （SDBS））. They were characterized using Fouriertransform infrared spectroscopy （FT-IR）. In our study, we found that carboxyl ofCNTs using the aqua regia were realized. At first, the purified CNTs using6M HNO3and surfactant were treated, the surface of CNTs was loaded anions, it is moreconducive to the preparation of CNTs/rare earth hydroxide.Secondly, to prepare strong fluorescent intensities of CNTs/Eu₂O₃complexes,with the help of the orthogonal experiment we explored the ratio of the purified CNTsand nitric acid europium （Eu（NO₃）₃）, the type and amount of surfactant, the time ofultrasonication, the temperature and time of reflow. Then thermogravimetric（TG）analysis of the purified CNTs and CNTs/Eu（OH）₃complexes was performed,indicating that the decomposition temperatures of the Eu（OH）₃/CNTs nanocompositescould be500°C. The nanocomposites were calcined at300～1000°C for4h, it is veryinteresting to discover the fluorescent intensities of emission bands increase with theincreasing of calcination temperature. And then the as-prepared nanocomposites’characterization are investigated in detail by means of such techniques as the analysisof scanning electric microscopy （SEM）, transmission electron microscopy （TEM）,fourier transform infrared spectroscopy （FT-IR）, X-ray diffraction （XRD） andfluorescent spectra. In our study we found that the mass ratio of the purified CNTsand Eu（NO₃）₃was about5.0wt%, the emission peak of Eu₂O₃/CNTs nanocompositesat650nm is stronger than that of other peaks. The as-prepared Eu₂O₃/CNTsnanocomposites calcined at620°C and1000°C exhibit a very strong emission bandat around540and580nm, due to the⁵D0â†'⁷Fj（j=0,1） forced electric dipoletransition of Eu³⁺ions. In turn, the emission spectra showed a slight blue shift.Thirdly, in order to explore high temperature sensitive fluorescence of other rareearth oxides/CNTs, CNTs/Tb₄O₇complexes were prepared. And then the as-prepared nanocomposites’ characterization are investigated in detail by means of suchtechniques as the analysis of scanning electric microscopy （SEM）, transmissionelectron microscopy （TEM）, fourier transform infrared spectroscopy （FT-IR）,thermogravimetry （TG）, X-ray diffraction （XRD） and fluorescent spectra. As the resultsshown that the mass ratio of purified CNTs and TbCl3was about25.0wt%, theemission peak of the Tb₄O₇/CNTs nanocomposites is stronger. The as-preparedTb₄O₇/CNTs nanocomposites calcined at400⁶00°C exhibit a very strong emissionband at around485nm and530nm, due to the⁵D₄â†'⁷Fj（j=5,6） forced electric dipoletransition of Tb3+ions. Nevertheless, the as-prepared Tb4O7/CNTs nanocompositescalcined at700°C exhibit a most strong emission band at around500nm, due to the⁵D4â†'⁷F5forced electric dipole transition of Tb3+ions. In turn, the emission spectrashowed a slight blue shift.Then, with assistance of grinding, ultrasonication dispersion and pullingfilm-forming method for preparing films of calcined super-fluorescent Eu₂O₃nanotubes. In our Study, we discoverdd that the poly（methyl methacrylate） as theforming-agent, the as-prepared films can not keep a good fluorescence, and lessmechanical.