Study On The Preparation And Kinetics Of Nanometer-Magnesia

The properties and application of nanometer magnesia have been briefly reviewed in this paper. Both the progress in the research and the synthesis of nanometer magnesia has been remarked, and the basic theory of nanometer powder has been discussed. According to conclusion of the mono-factor experiments, the multifactor orthogonal experiments have been applied in order to analyze systematically. The optimum processing conditions and the key factor in preparation of nanometer magnesia are achieved. TG/DTA/DTG, XRD, TEM and FI-IR techniques were used to characterize the samples. Drying methods, kinetics is studied. The main contents and results are as follows:The decompounded-experiments of nanometer magnesium hydroxide demonstrate that the transformation of crystalloid happens in the temperature range from about 250 C to 350 C; magnesium hydroxide absolutely decompounds at 400 C; the higher the calculations temperature is, the bigger the diameter of nanometer magnesia is.To determine influence of technical conditions on Product diameter, the influences of concentrations , molar ratio, reaction temperature and time on average size were investigated by means of multifactor orthogonal experiments. The results of experiments indicated that product diameter was mostly influenced by concentration of reactants, reaction temperature, followed by molar ratio of reactant and reaction time. According to conclusion of the monofactor experiments and multifactor orthogonal experiments, The optimum processing conditions in preparation of nanometer magnesia: C(MgCl2-6H20)=2.1mol/L , n(CO(NH2)2):n(MgCl2'6H20)=5:l, reaction temperature 95癈 and reaction time 3h.Under these conditions MgO nano-Particles with average crystalline diameter of 4nm were obtained.The result of drying experiment indicates that agglomeration degree of nanoscale magnesium oxide particles is relevant with solvent-replacement method. As for the same drying method, agglomeration degree mitigated by the following order: water-washing, water+N,N-dimethyl acetamide washing, alcohol-washing, water-washing + butyl alcohol azeotropic distillation and alcohol-washing + butyl alcohol azeotropic distillation.the diameter of MgO crystalline is affected on drying method. As for the same drying method, the diameter of MgO crystalline mitigated by the following order: water-washing, alcohol-washing,water+N-N-dmiethyl acetamide washing, water-washing + butyl alcohol azeotropic distillation and alcohol-washing + butyl alcohol azeotropic distillation.The TG and DTA techniques were used to research the decomposition kinetics of Mg(OH)2.The decomposition mechanism and kinetics equation were investigated according to Coats-Redfern and Doyle methods, the activation energy was about 126.6kJ/mol, and the equation can be depict as follow:By means of the kinetic theory, the dynamics equation of nanometer MgO grain growth is obtained, the activation energy was about 108.8kJ/moL and the equation can be depict as follow:...