Process Study On Preparation And Surface Modification Of Nanometer Magnesia In Precipitation-Transforming-Method

The properties, applications and research situation at home and abroad of nanometer magnesia have been presented in this thesis. The theoretical analysis of preventing agglomeration mechanism in the process of preparing nanometer magnesia particle using precipitation-transforming-method (PTM) and the theoretical foundation for surface modification of nanometer MgO are mainly discussed. A set of craft for preparation of free-agglomeration nanometer MgO particle has been provided. In this thesis, the technology of preparing nanometer magnesia in PTM was further studied, and then surface modification of nanometer magnesia particle was discussed. Hydraulic reaction and drying process were focused on in the preparation process. Both inorganic and organic surface modifications for nanometer MgO were carried out using different modifiers, and the optimal process conditions have been selected by mono-factor and multi-factor orthogonal experiments respectively. A series of hydrophilic and hydrophobic nanometer magnesia particles have been fabricated.The experimental results are shown as follows:(1) It is possible that a further optimization for preparation of nanometer MgO in PTM with magnesium chloride and sodium carbonate as materials and PVA as the disperser. The optimal process conditions are: the amount of PVA added into the reactants is 10~13mL, the precipitant is washed by PVA distilled water(3%~5%wt PVA) and ethanol, the mixing order is optimal style, the drying time is 10min in microwave oven, the calcination is at 550C for 160min. Under these conditions, theaverage diameter of nanometer magnesia particles is about 7.5nm.(2) After inorganic modification with aluminum chloride, the dispersity and stability of nanometer magnesia particles in both the distilled water and ethanol become better, and the ability of UV shielding is greatly improved.(3) Nanometer magnesia is turned to hydrophobic after surface modification with sodium stearate. The feasible conditions are: the dosage of modifier reagent is 18%, the modification temperature is 50C, the time is 35min, pH is 10.6, and the hydrophobic value is 0.492.(4) Nanometer magnesia modified with titanatic coupling agent by wet method and dry method is hydrophilic. The optimum conditions of the dry-way modification are : the content of modifier is 3%-5%, the modifying time is 2h, the rotating speed of ball milling is 240~300rpm. The optimal conditions of the wet-way modification are: the reaction time is 30min, the modifier addition is 10mL, the temperature is 50C. The chemical bond occurred between the modifier and nanometer magnesia particles.Jiang Hongmei(College of chemical engineering) (Directed by Prof. Guo Renmin)...