Morphology Control And Preparation Of Layered Double Hydroxides

Controlled synthesis of inorganic materials of specific morphology, orientation, organization, complex form, and hierarchical structure has drawn a lot of attention in materials science, especially on the Layered double hydroxides (LDHs), a kind of new functional material. The strategy of using organic templates or modifiers with complex functionalization patterns to control the nucleation, growth, and alignment of crystals has been widely adapted for the synthesis of a variety of inorganic materials with complex forms. This dissertation focuses on the morphosynthesis of some inorganic materials assisted by organic additives, and the main results are as follows, and the XRD, SEM and TEM were used to characterize the material and its formation process theory.In the first parts, controlled synthesis of LDHs was studied on the optimized parameters of process. Single drop method, double drips method, hydrothermal, gas liquid systems were involved to prepare LDHs. During the study, we found Hydrothermal System better than other methods, and the gas Liquid System was the worst one. Then the conclusion of alkaline also had a big effect on the growth of LDHs, when changed the alkaline between (NH₄)₂CO₃, NaOH (Na₂CO₃), urea, hexamethyleneteramine (HMT). If the ethylene diamine tetra acetic salt (EDTA-Na) and ethanol was added to the combination system, ethanol takes a good job as a dispersion media.In the second part, added the cetyltrimethylammonium bromide (CTAB) to the system, the results showed that the CTAB system was a very effective crystal growth to guide the growth of LDH crystals to various morphologies with different reaction Conditions. By changing reaction conditions, such as the ratio of Ni/Al concentration,value , in the reaction temperature, time, especially, the rosette-like and spatulate-like NiAl- LDH crystals were synthesized, and the formation mechanism was related to the selective interaction between the organic-inorganic interfaces gained through carboxyl and Ni²⁺ , which resulted in preferential growth along some specific crystallographic directions. When increased with raising ageing temperature and time, the rosette-like LDH would like change to spatulate-like. And the formation of spatulate-like NiAl-LDHs crystals was ascribed to the directing of surfactant micelle.In the third part, crystallization of LDH was studied in another surfactant sodium alginate (SA). The SA system could induce LDH crystals to spherical imaged in the SEM photos. Also with different reaction conditions the LDHs showed different from the tradition morphology. Moreover, and the spherical-like crystal has a virtue of high-temperature stability, because when baked the LDH to LDO, the shape of spherical does chance any more.In our work, as the precursor LDHs films were prepared with direction CTAB and SA, as we put forward the substitution by Ni in hydrotalcite layers to synthesize the film of NiAl-LDHs, which are potential precursors of catalysts for carbon fiber growth. Then, carbon fibers were synthesized via the catalytic chemical vapor deposition (CCVD) method over these catalysts in quartz reactor. As well as the growth mechanism of the LDHs films was also discussed. Different guiding agent in the same conditions, the LDH films gained different configuration, and affect the morphology of carbon fibers directly.