Synthesis And Character Of Polymorphic Palladium, Tin, And Cerium Nanomaterials

Nanoscience and technology is based on the science of designing and manipulating materials at the level of atoms, molecules, and supermolecular structures. It emerged in the 1980s and has been increasingly developed. Nowadays, research on nanostructured materials is a rapidly growing field of science. Nanostructured materials exhibit novel physical and chemical properties and potential applications. Among of them, polymorphic materials are of great importance because of their great potential for testing and understand fundamental concepts and application. Metal palladium, as an important noble metal, possesses critical status in catalyst field. Preparing polymorphic palladium nanomaterials are significant for the development of catalyst domain. SnO₂ has been investigated many years ago and used extensively in the semiconductors. The syntheses and researches of polymorphic SnO₂ nanomaterials will help to understand fundamental and that contributes physical principles of semiconductors to development and application of them. Moreover, Cerium as an critical thulium has been researched and applied extensively in hydrogen storage materials, catalyst domain, photoelectric parts, functional ceramics, thermoelectric materials, fuel cells, certain magnetic materials, various allay steels and non-ferrous metals. Synthesis of polymorphic cerium nanomaterials will help to understand properties, development and application of them.The major contributions of this dissertation include the following aspects:1. One-step synthesis of porous palladium nanostructures and nanoparticles by H2+He arc plasma methodPorous palladium nanostructures were prepared on a copper sheet previously fixed over the plasma high-temperature area by H2+He arc plasma method. However, dispersed palladium nanoparticles with diameters in 50-90 nm were obtained on the inner wall of vacuum chamber. SEM, TEM, EDXA, XRD and BET were employed to characterize the palladium porous materials. SEM images show that porous palladium nanostructures are composed of spherical particles with diameters of 35±3 nm. This special structure with large surface to volume ratio can be recycled easily for application in the field of catalysis. Further, we discussed the formation principle of porous palladium nanostructures and palladium nanoparticles.2. Hydrothermal synthesis of SnC>2 hollow microspheresSnO2 hollow microspheres have been synthesized by hydrothermal method. X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) were used to characterize such hollow microspheres. SEM image shows that SnC>2 microspheres with diameters of 0.5-1 urn are composed of SnC>2 nanoparticles with about 15 nm in diameter. Some broken microspheres indicate the hollow spherical structure. XRD shows that SnCh hollow microspheres have tetragonal structure. Further, we discussed the formation principle of SnC>2 hollow nanostructures.3. Hydrothermal Method to Synthesize Single Crystal Ce(OH)CO3 and CeO2 with Triangular Structuresingle crystal Ce(OH)CO3 with triangular structure were synthesized in the presence of surfactant cetyltrimethylammoniurn bromide (CTAB) by a simple method. Then as-synthesized Ce(OH)CC>3 was calcined to produce single crystal CeO2 with triangular structure in air at 650 °C for 7 h. SEM images of Ce(OH)CO3 and CeO2 indicate the triangular structure. XRD shows that Ce(OH)CO3 have hexagonal structure and CeC>2 have face-cubic structure. TEM images and selected...