Preparation And Characterization Of Peculiar Morphology Magnesium Carbonate And Magnesia Powders

In this dissertation, magnesium carbonate of the single phase composition powders contains no crystal water and magnesia powders that with the peculiar morphology and different properties have benn prepared respectively with sodium citrate and chitosan by hydrothermal treatment methods and with magnesium chloride as salt,urea as precipitator The effects of the amount of sodium citrate, the amount of chitosan, salt-alkali ratio, hydrothermal temperature and hydrothermal time on magnesium carbonate powders and magnesia powders were investigated systemically by SEM, XRD and size analysis.The magnesium carbonate of single phase composition powders contains no crystal water with peculiar 3D flower shape and spherical shape morphology can be prepared on the condition of different hydrothermal temperature and hydrothermal time by changing the amount of sodium citrate and the salt-alkali ratio.The results indicate that the particle size of 3D flower shape magnesium carbonate is about 15μm and the the particle size of 3D spherical shape magnesium carbonate is about 20μm.The Magnesia powders can be prepared after magnesium carbonate calcined at high temperature.The basic morphology of magnesia keeps the same as that of magnesium carbonate.The magnesia powders with peculiar honeycomb shape can be prepared on the condition of the special hydrothermal temperature by changing hydrothermal time.If the hydrothermal temperature is too high,it may cause the decomposition of chitosan,the expected product can not be prepared. And the peculiar honeycomb shape magnesia is made of the minute particles.The results indicate that the particle size of the peculiar honeycomb shape magnesia is about 10μm.As the hydrothermal time prolonging,it can be seen the inside of the product is hollo w,and the outer casing is made of the minute particles.On the basis of the results, to explore the growth mechanisms of the magnesium carbonate and magnesia, the complexation of sodium citrate and chitosan with Mg2+and the surface energy of the powders have been analyzed, so the conclusion has been put forward.