Studies On Preparation And Modeling Of CuO/SiO₂ Nanocompsite By Adsorption Phase Reactor Technology

In this dissertation, Synthesis of CuO/SiO₂ nanocomposite materials in a nanoreactor formed by the water-rich adsorption layer on the surface of SiO₂ was studied. First, the research, characteristic and application of CuO nanoparticles and nanocomposite materials were reviewed. According to whether nanoreactor was used in the preparation process of nanoparticles, the author divided the preparation methods of nanocomposite materials into two kinds: traditional methods and advanced methods(mainly involve the micro scale reaction technolygy). The author divided micro scale reaction technology into soft constraint and hard constraint in terms of boundary properties, and independently generalized its principle, characteristic and application. The advantage and disadvantage microscale reaction technology were also generalized contrasted with traditional methods.Based on the generalization of abroad literatures and research findings, the principle and characteristic of adsorption phase nanoreactor technology were represented detailed, and pointed out the formation of adsorption layer and reaction place were the two most important factors in this technology. The evolvement of adsorption phase reaction technology was summarized in two points of view for adsorption and reaction. Then the research orientation and experiment strategies were proposed based on research findings which had been achieved.Aiming at the new experiment system and the two elements in adsorption phase reaction, the primary project was proposed. And adsorption capacity mensuration experiment, solvent substitution experiment and reaction-adsorption experiment shows that the water adsorption layer exists on the SiO₂ surface and plays as a place reaction mainly occurring. XRD analysis showed that CuO crystal existing and the grain size could be calculated by Scheller formula.For the reaction system composed by Cu ions as precursor and NaOH as the succeeding reactant, the experiments were designed according to adsorption andreaction process. Complexometric titration method, TEM, XRD and EDAX were used to study the whole process. Result showed: (1) The adsorption of Cu ions can only occur while the bulk phase is quite different from the SiC>2 surface;(2) The three-region distribution model of Cu2+ in this system has been proposed according to the adsorption data;Adsorption of Cu ions in adsorption layer will be enhanced by temperature rising;(3) The adsorption capacity and Cu ratio content in incomplete reaction product will both increase with water concentration rising, which is considered to be the result of thickening of adsorption layer;(4) When the sodium hydroxide was added in step by step, the Cu ions in adsorption layer react first because of its high activity, and the Cu ions on SiO2 surface react at last;(5) The grain of CuO crystal mainly controlled by the thickness of adsorption layer and the supersaturation degree in it.The differential equation model has been built and solved aiming to the reaction diffusion and crystallization process. Analysis showed: (1) The diffusion of NaOH in two phases is the controlling step in the whole process. The feed rate will change the diffusion driving force and then make the reaction rate change;(2) The increase of adsorption layer thickness will mainly decrease the product concentration. (3) The feed rate speeding up and amount of NaOH increment will make CuO grain size decreasing, which is considered to be the simple effect of supersaturation. (4) The change of adsorption layer thickness will make both supersaturation and crystallizer volumes vary. Though the increase of supersaturation would make crystal rate of unit volume rise, CuO grain size still becomes smaller because of the decrease of crystallizer volumes.At last, the work in the dissertation was generalized, and the problems which still need to discuss in paper were represented.