Study On Nano-magnesia Preparation Technology

The properties, applications and research situation at home and abroad of nanometer magnesia have been presented in this thesis. The technology of nano-magnesia preparation and the using for surfactant of nanometer MgO are mainly discussed. According to the quality of the raw material and the demand of the production,two sets of craft for preparetion of nanometer MgO particle have been provided. In this thesis, the technology of prearing nanometer magnesia through direct conversion method was further studied. The process for preparaing basic magnesium carbonate, drying process and calcining process were focused on in direct conversion method. Surfactant, drying and the optimal process conditions have been selected by mono-factor and multi-factor orthogonal experiments respecticely. Ammonium lixiviate process and precursors preparaed process were mainly studied in complete battering emulsion method.The experimental results are showen as follows:(1) It is possible that the preparation of nanometer MgO in direct conversion method with magnesia and salvolatile as raw materisls and A17 as the disperser. The optimal process conditions are: reaction temperature was 76℃, reaction time was 90 min, (NH₄)₂CO₃ concentration was 0.35mol/l, mole ratio of MgO and (NH₄)₂CO₃ was 1:1.3, the amount of surfactant was 0.5%o of total amount of reactants. The precursors ware dried at 80℃for 2h under vacuum and calcined at 600℃for 1.5h.(2) It is possible that the preparation of nanometer MgO in complete battering emulsion method with lightly calcined magnesia and ammonium sulfate as raw materisls and A17 as the disperser. The optimal process conditions are: reaction temperature was 80℃reaction time was 90 min and (NH₄)₂SO₄ concentration was 1.2mol/l in ammonium lixiviate process. Reaction temperature was 75℃, reaction time was 90 min, (NH₄)₂CO₃ concentration was 0.35mol/l, mole ratio of MgSO₄ and (NH₄)₂CO₃ was 1:1.3, the amount of surfactant was 0.5‰of total amount of reactants. The precursors ware dried at 80℃for 2h under vacuum and calcined at 600℃for 1.5h. The nanoparticles and its precursors were characterized by XRD, TEM, SEM, TG-DTA, ETDA etc. The results indicate that MgO nanocrystals which has been obtained by direct-conversion method are well dispersed with a narrow size distribution, an average size is of 65nm and specific area is of 144.99m²/g. MgO nanocrystals which has been obtained by complete battering emulsion method are well crystaled , an average size is of 150nm, specific area is of 92.65m²/g and purity of nano-MgO is of 99.5415%.A kinetics equation debeloped from the early stage data agreed well with the Core-Shrinking Model. The apparent activation energy was 57.41kJ/mol which indicates that the leaching process is controlled by the surface chemical reation. A kinetics equation debeloped from the final stage data agreed well with the Crank-Kinstelin-Browhetein Model. The apparent activation energy was 57.41kJ/mol which indicates that the leaching process is controlled by the chemical reation.