关键词: 氧化镁;水热;溶解结晶;螺旋位错

Abstract: Active magnesium oxide prepared from low-temperature calcination of magnesite was used as raw material,and in order to study the effects of anhydrous magnesium sulfate on magnesium oxide hydrothermal products,we conducted this experiment under 160℃ of hydrothermal synthesis temperature and 400 r/min of stirring speed. When the molar ratio of magnesium oxide and magnesium sulfate is 10:1 ,hydrothermal product after six hours was hexagonal flake magnesium hydroxide with high purity and good crystallinity. When the molar ratio of magnesium oxide and magnesium sulfate is 2. 5: 1, hydrothermal product in the first three hours was hexagonal flake magnesium hydroxide,and with the increase of time,there was more and more basic magnesium sulfate whisker appeared. When the molar ratio of magnesium oxide and magnesium sulfate is 10:7 ,hydrothermal product in the first 50 min was hexagonal flake magnesium hydroxide,then small particles dissolved and formed crystal nucleus of basic magnesium sulfate,while large particles of hexagonal flake magnesium hydroxide formed MgSO4 ·5Mg (OH)2 ·3H2O together with MgSO4 and H2O. The growth unit Mg-O6 entered into the sunken of two-dimensional steps formed because of screw dislocation in the growth direction,which prompted the stable growth of whisker along the screw dislocation direction. With the increase of anhydrous magnesium sulfate concentration,there was more and more basic magnesium sulfate whisker in the product,and it would be a short time to form basic magnesium sulfate whisker.

Key words: magnesium oxide;hydrothermal;solubility and crystallization;screw dislocation