Microwave Synthesis, Characterization And Properties Of Rare Earth Compounds With Mocro/Nano-structures

The rare earth elements have special atomic structure, with many unpaired electrons in the inner layer 4f orbitals. The metals are very lively, easily to lose electrons, high atom magnetic moment, and extremely rich electron energy level. Rare earth metals can react with almost all elements, forming compounds of various valence coordination number(from 3 to 12). The rare earth compounds have been widely used in fluorescence, gas storage, adsorption, catalysis, sensors and magnetic fields. But some factors such as temperature, time, pH, can affect in the synthesis process, the controllable synthesis of rare earth compounds is still a challenge.At present, there are many methods to prepare rare earth compounds nanomaterials, such as high temperature solid method, solvent thermal techniques, sol-gel method, coprecipitation, and thermal decomposition, etc. But there are drawbacks of above methods, such as environmental pollution, high cost, harsh reaction conditions or expensive equipment or conducive not to product on a large scale. Ultrasonic produces high strength mechanical and thermal effect because of its cavitation effect. Microwave improves the reaction efficiency, and reduces the reaction time by producing high efficiency heating and dielectric heat. Ultraviolet light has the effect on the chemical synthesis because of photochemical reaction. Microwave combined with ultrasound or ultraviolet light in chemical reaction, is not equal to simple math together, but the function has stronger synergy effect. Microwave irradiation, ultrasound irradiation and ultraviolet(UV) each has its advantages, but the three synergy in the aspect of rare earth materials synthesis haven’t been reported. Therefore, microwave combinated with ultrasound or ultraviolet or three together, will achieve the enhancement purpose to regulate the structure and morphology. This paper studied the microwave chemical application in micro/nano material synthesis. Microwave irradiation, ultrasound irradiation, and ultraviolet, the three kinds of technology were discussed for the effect of micro/nano structure and morphology, which would help to provide a certain theoretical basis and method of route for the synthesis of other rare earth micro/nano material.The main research content of this paper are as follows:(1)Microwave hydrothermal synthesis, characterization and properties of rare earth stannate spherical nanoparticlesBy microwave hydrothermal method, rare earth stannate spherical nanoparticles with reaction of gadolinium nitrate and stannic chloride, to put Gd2Sn2O7 as a typical sample, was quickly synthesized under 200 oC for 60 min. X-Ray diffraction(XRD), fourier transform infrared(FT-IR) spectroscopy, scanning electron microscopy(SEM), transmission electron microscopy(TEM), energy-dispersive spectroscopy(EDX), high-resolution transmission electron microscopy(HRTEM), selected area electron diffraction(SAED),, as well as SQUID magnetometry were used to characterize the products. In the typical Gd2Sn2O7 sample, results showed that the spherical-like nanoparticles were about 50 nm in diameter. The effect of reaction parameters such as temperature, reaction time, pH and types of alkali on the preparation was briefly investigated. Possible formation mechanism of Gd2Sn2O7 was proposed. Its magnetic performance and luminescent properties doped Eu3+, were explored. Using the same similar methods and steps, rare earth stannates [Ln2Sn2O7(Ln =Y, La- Lu)] nanocrystals were successfully prepared.(2) Microwave-hydrothermal synthesis, characterization and upconversion luminescence of Gd(OH)3 nanorodsGadolinium nitrate and sodium hydroxide as raw materials, through a facile and rapid microwave-hydrothermal synthesis method without using any surfactants or templates, rice-like Gd(OH)3 nanorods were successfully prepared for the first time under 120 oC for 60 min. Results showed that the nanorods were with an average length of 400 nm and an average diameter of 50 nm. The effect of reaction parameters such as reaction temperature and time on the preparation was briefly investigated. When the rice-like Gd(OH)3 nanorods was codoped with Yb3+ and Er3+, strong upconversion emissions could be observed under the excitation of 980 nm laser, and the calculated CIE color coordinates fell within the yellow region, which may be potential candidate for optical materials.(3) Microwave/Ultrasound/Ultraviolet light-assisted synthesis, characterization, formation mechanism and magnetic properties of hexagonal DyPO4·1.5H2 O microcrystalsWithout using template or surfactant under 90 oC for 20 min, a simple, fast and facile microwave(MW)/ultrasound(US)/ultraviolet light(UV)-assisted method was designed for the preparation of DyPO4·1.5H2 O microstructures. Results showed that hexagonal DyPO4·1.5H2 O microcrystals were broom-sheaf-like bundle microstructures with the lengths of 5-6 μm and widths of 2-3 μm under microwave irradiation. No product were obtained when ultrasound(US) or ultraviolet light(UV, 365 nm) was used, respectively. Needle-shaped particles were found to be formed in the presence of MW and US. Interestingly, the broom-sheaf-like structures can self-assemble into flower-shaped structures upon MW and UV, whereas combination of UV with US has been investigated for DyPO4·1.5H2 O microstructures changing from broom-sheaf-like microstructures to flower-like with needle-shaped structures. A possible mechanism responsible for the formation of microstructures with various morphologies was proposed. And its magnetic property was explored.(4) Microwave synthesis and characterization of the compound with gadolinium and 4, 4-dihydroxy diphenyl ketoneBy the trinity microwave method, under the reaction conditions of microwave and microwave combined with ultraviolet(UV) at 80 oC for 20 min, with gadolinium nitrate and 4, 4- dihydroxy diphenyl ketone as raw material, the compound with gadolinium and 4, 4-dihydroxy diphenyl ketone was obtained. The XRD, FT-IR, SEM, TEM and TG-DTG were used to characterize the the compound. Results showed that the product was amorphous using microwave as well as the combination of microwave and ultraviolet(UV). No typical characteristic absorption peaks appeared. The layout of the synthetic product was mesh structure. Contrast figures of the product under microwave and combination of microwave and ultraviolet(UV) could be seen that their morphologies were not significantly different, very similar, indicating that synthetic product had certain resistance to ultraviolet(UV).