The Synthesis Of Group ⅢA And Iva Oxide Nanomaterials And Their High-pressure Studies

Oxide nanomaterials have great technological importance in many applicationfields, such as catalysis, luminescence, diluted magnetic semiconductors, and fineceramics, etc.. The physical and chemical properties and performances of the oxidenanomaterials are close related to their shape and size. In pursuit of desirablematerials with versatile properties, the controllable preparation of oxide nanomaterialswith tailored morphologies (size, shape, and spatial configuration) has become one ofthe most important research focus in nowadays materials science and technologycommunity.High pressure studies on nanomaterials have also attracted extensive researchinterest. It can be expected that low dimensional systems with small sizes under highpressures will bring about novel phenomena and effects that are not encountered intheir bulk counterparts. It may offer new opportunities to reveal the intrinsic origin ofthe peculiar properties of nanomaterials, and hence to establish new physical conceptsand theories to guide the preparation of novel materials.In this dissertation, the group IIIA and IVA oxide nanomaterials are taken as a casestudy. By employing the solvothermal alcoholysis method, the factors and parametersaffecting the morphologies of the products are systematically investigated. Thegrowth mechanism of the products with specific morphologies have been elucidated.In succession, the high pressure studies on the prepared group IIIA and IVA oxidenanomaterials are carried out, by using the diamond anvil cell (DAC) technique. Theevolution behaviors of the lattice and the hydrogen bond are investigated in detail.The main results obtained are as follow:1. The nanosheets of AlOOH have been prepared via the solvothermal alcoholysis method by using anhydrous AlCl3and methanol as the reactants. The surfaces of theprepared nanocrystallites are covered with hydroxyl (-OH). Due to the layeredstructure of AlOOH lattice, the interactions of the hydroxyl groups between the layerslead to the formation of the sheet-like morphology of the final product.2. The hyperbranched hierarchical nanoarchitectures of GaOOH have been preparedvia the solvothermal alcoholysis method by using anhydrous GaCl3and methanol asthe reactants. The time-dependent morphology evolution of the preparednanoarchitectures strongly indicates that the peculiar hyperbranched morphology maygrow due to the crystal splitting mechanism.3. The nanospheres of silica (SiOx) have been prepared via the solvothermalalcoholysis method by using SiCl4and methanol as the reactants. A variety ofsurfactants have been tested to control the size and dispersity, among which CTABand P123seem to be effective.4. The nanocrystals of germanium oxide (GeOx) have been prepared via thesolvothermal alcoholysis method by using GeCl4as the precursor. However, sphericaland spindle-shaped nanostructures are alternatively obtained, when methanol orethanol is adopted as the other reactant.5. By using in situ angle-dispersive synchrotron radiation X-ray diffraction technique,the high pressure studies on the hexagonal prism-like nanorods of α-GaOOH havebeen carried out. α-GaOOH sustains its orthorhombic structure when the pressure islower than23.8GPa. The compression proceeds mainly by shrinkage of the voidchannels of the crystal structure. Anomaly has been found in the compressionbehavior to occur at14.6GPa, which is concomitant with the equatorial distortion ofthe GaO3(OH)3octahedra. The fittings of a second order Birch-Murnaghan equationof state to the p-V data in different pressure ranges indicate the discontinuity of theelatic properties. As the pressure is increased to about25.8GPa, a first-order phasetransformation takes place, which is evidenced by the abrupt decrease in the unit cellvolume and b and c lattice parameters.