Synthesis, Structure And Crowth Mechanism Of Borate Nanoma Terials

Borates have extremely important potential applications in strengthencomposite materials such as metal, plastic etc, and of lubricant, and inluminescent materials in the future. Therefore,considerable attentions havebeen devoted to the fabrication of borates materials, especial nanostructuredborates. Among strategies of the fabrication of materials,template-mediated techniques have been demonstrated to be very effective.This thesis was focused on the fabrication of borates materials viatemplating Process. The main results are summarized as follows:1. Using CTAB or glucose as template, the aluminum borate (Al4B2O9)nanorods were synthesized by the sol-gel method with aluminumtri-sec-butoxide boric acid as reactant. Al4B2O9 nanorods with diameters of15²0 nm and lengths of 200³00 nm were prepared by tuning theexperimental factors. The structure and morphologies of the synthesizedsamples were investigated by XRD,SEM and TEM. Based upon theexperiment results,the potential mechanism of Al4B2O9 nanorods wasproposed: In aqueous solution, CTAB could form rod-like micelle, theAl(OH)4- phase slowly grow along the surface of CTAB micelle, andfinally become nanorods. During the calcination at 750 oC, Al4B2O9nanorods were fabricated by self-catalytic growth mechanism. Whileglucose as template, complex network structure was formed after glucose and boric acid reacted. Source of aluminum was then well dispersed in themiddle of the network.2. Mesoporous magnesium borate microspheres have been synthesizedvia precipitation reaction in aqueous solution of Na₂B₄O₇.10H₂O andMg(NO3)₂.6H₂O with sodium dodecyl sulfate(SDS) as template. Themicrospheres were characterized by SEM,TEM,FT-IR and nitrogenadsorption-desorption isotherm. The results showed that a pore structurewith larger pore diameter (10⁵0 nm) was synthesized. Nitrogenadsorption-desorption isotherm showed a Langmuir IV category which isrelated to mesoporous materials.and the BET surface area and pore volumewas 53.03 m²/g and 0.37 m³/g respective . The potential mechanism ofmesoporous magnesium borate microspheres was followed: In aqueoussolution, SDS could form a sphere (oil-in-water emulsion) micelle, thenMg2+ adsorbed on the surface of the sphere. The reaction of Mg2+ andNa2B4O7 proceed along the sphere. After the surfactant was removed bycalcination, magnesium borate sphere with meso-pores was prepared.3. Magnesium borate of lamellar nanostructures was fabricated by lowtemperature hydrothermal synthesis with oil acid as template or themodifying agent. The sample was characterized by XRD丄SEM丄FT-IR andN2 adsorption-desorption isotherm. According to the FT-IR result, thegrowth mechanism of lamellar-structural magnesium borate was proposed.Applation oil acid as the modifying agent, calcium borate nano-materialwas prepared by precipitation reaction too.