Study On Nano-Aluminates And Carbonates Of Sr And Ba: Controllable Synthesis And Properties

Nano-science and technology is one of the most advanced research fields in 21th century, and the investigations on nano-materials and nano-structures are of particular importance. On the basis of the significant effects of nano-structure on nano-materials' properties, the interest of this dissertation is focused on preparation and property investigation of nano-materials. MAl2O4 nano-particle, MCO3 nano-wire and MAl4O7 nano-sphere (M = Sr or Ba) were fabricated successfully. The relationship between nano-structure and property has also been investigated in detail. In general, novel preparation methods and some new properties were provided to synthesis and application of these nano-materials. The main contents of this report are as follows:Using amorphous hetero-nuclear complexes as precursors, pure spinel SrAl2O4 and BaAl2O4 nano-particles were successfully synthesized at low calcinations temperature, which was about 500℃ lower than that in conventional methods. Nano-structure of these nano-particles showed high stability even at 1000℃, indicating that high-temperature materials can be easily prepared at a relatively low temperature by this method.The investigation indicates that nano-structure has great effect on the optical property of SrAl2O4 and BaAl2O4. A simple reduction process can make these nano-particles show uniform adsorption throughout UV-VIS-NIR, in spite that their composition, crystal structure and morphology did not change after this process. Further study indicates that the unique optic performance is related to the concentration of oxygen vacancy in nano-particles.Uniform SrCO3 and BaCO3 nano-wires with high aspect ratio of over 1000 were successfully prepared using a simple gas-liquid reaction. And a formation mechanism described as "preferentially growth→self-assemble→restructure" has been proposed. It has been found in this work that one-dimensional structure has great effect on the catalytic property of nano-materials. The activation temperature of formaldehyde and ethanol decreased 230℃-300℃ when catalyzed by SrCO3 nano-wires. Our results showed that nano-wires had obviously higher catalytic activity than nano-particles, and such an improvement in the catalytic activity could be attributed to the different distribution of active centers on nano-wires and nano-particles.MAl4O7 (M = Sr,Ba) porous nano-spheres were successfully prepared by hydrolyzing of SrAl2O4 and BaAl2O4 nano-powder in ethanol-H2O solution, and the interior structure of these nano-spheres can be easily prepared by controlling concentration, heating mode and heating time. Based on the results obtained above, a formation mechanism described as "template-in situ reaction" was proposed.